{"pdfData":[[{"bbox":[86,79,335,89],"type":"text","angle":0,"index":0,"text":"数据库（Database）是按照数据结构来组织、存储和管理数据的仓库。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"f902fa0c-96e3-4a73-877f-b7057439e1cb","page_size":[595,841],"block_position":"0-0"},{"bbox":[86,95,405,105],"type":"text","angle":0,"index":1,"text":"每个数据库都有一个或多个不同的 API 用于创建，访问，管理，搜索和复制所保存的数据。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"a6ba50c5-c255-44fc-b79d-1752c312379d","page_size":[595,841],"block_position":"0-1"},{"bbox":[86,111,341,121],"type":"text","angle":0,"index":2,"text":"我们也可以将数据存储在文件中，但是在文件中读写数据速度相对较慢。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"2c7990e3-ce09-4266-8b46-fab7c231380c","page_size":[595,841],"block_position":"0-2"},{"bbox":[86,126,501,153],"type":"text","angle":0,"index":3,"text":"所以，现在我们使用关系型数据库管理系统（RDBMS）来存储和管理大数据量。所谓的关系型数据库，是建立在关系模型基础上的数据库，借助于集合代数等数学概念和方法来处理数据库中的数据。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"7516513d-47e8-4cde-b53e-bd1349bcf7c6","page_size":[595,841],"block_position":"0-3"},{"bbox":[88,163,200,183],"type":"title","angle":0,"index":4,"text":"# RDBMS 术语","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":0,"id":"75d440d4-c4bc-4b16-9a4c-8fe13d25d7f1","page_size":[595,841],"block_position":"0-4"},{"bbox":[87,191,348,201],"type":"text","angle":0,"index":5,"text":"在我们开始学习MySQL 数据库前，让我们先了解下RDBMS的一些术语：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"d3b107dc-6073-435b-99a8-0c6a6799f2e4","page_size":[595,841],"block_position":"0-5"},{"bbox":[80,207,228,217],"type":"text","angle":0,"index":6,"text":"数据库: 数据库是一些关联表的集合。","id":"84f2fb9a-3e23-4f02-9c0a-ae3f42a34188","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-6"},{"bbox":[79,232,371,243],"type":"text","angle":0,"index":7,"text":"数据表: 表是数据的矩阵。在一个数据库中的表看起来像一个简单的电子表格。","id":"733d7d64-62be-48cc-a024-a79ac5a061d5","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-7"},{"bbox":[79,259,329,269],"type":"text","angle":0,"index":8,"text":"列: 一列(数据元素) 包含了相同类型的数据, 例如邮政编码的数据。","id":"ce8cee40-6025-4973-b1a9-ad00154b3e54","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-8"},{"bbox":[79,285,359,295],"type":"text","angle":0,"index":9,"text":" 行：一行（元组，或记录）是一组相关的数据，例如一条用户订阅的数据。","id":"898a874d-a2e0-457a-8e6e-c90fff466e37","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-9"},{"bbox":[79,312,327,322],"type":"text","angle":0,"index":10,"text":"冗余：存储两倍数据，冗余降低了性能，但提高了数据的安全性。","id":"11209d0c-85ab-4d73-b21d-a7f216d22f61","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-10"},{"bbox":[79,337,399,347],"type":"text","angle":0,"index":11,"text":"主键：主键是唯一的。一个数据表中只能包含一个主键。你可以使用主键来查询数据。","id":"9e9e88cc-ce55-489a-9e7e-3aa695268f44","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-11"},{"bbox":[80,363,199,373],"type":"text","angle":0,"index":12,"text":"外键：外键用于关联两个表。","id":"7cbd737a-052e-415e-b422-653223e712e3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-12"},{"bbox":[79,389,359,399],"type":"text","angle":0,"index":13,"text":". 复合键：复合键（组合键）将多个列作为一个索引键，一般用于复合索引。","id":"adbd51ee-a455-4d17-8279-61a7f0b24174","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-13"},{"bbox":[79,415,502,441],"type":"text","angle":0,"index":14,"text":"索引：使用索引可快速访问数据库表中的特定信息。索引是对数据库表中一列或多列的值进行排序的一种结构。类似于书籍的目录。","id":"04e39c46-a75f-4747-8ed9-3ba04e768b31","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-14"},{"bbox":[79,457,503,482],"type":"text","angle":0,"index":15,"text":". 参照完整性: 参照的完整性要求关系中不允许引用不存在的实体。与实体完整性是关系模型必须满足的完整性约束条件，目的是保证数据的一致性。","id":"9de0d293-ba14-42ac-b487-f4873aa66ac9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-15"},{"bbox":[79,498,201,509],"type":"text","angle":0,"index":16,"text":"表头(header): 每一列的名称;","id":"e72070bd-e30d-409c-bd17-37b89508ff44","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-16"},{"bbox":[79,525,242,535],"type":"text","angle":0,"index":17,"text":". 列(col): 具有相同数据类型的数据的集合;","id":"fb6f91b3-c0d0-4083-a77d-0557d5a36dd8","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-17"},{"bbox":[79,551,261,561],"type":"text","angle":0,"index":18,"text":"行(row): 每一行用来描述某条记录的具体信息;","id":"aa0106b8-b0bc-44c4-8fe4-cee93a5872f8","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-18"},{"bbox":[79,576,311,587],"type":"text","angle":0,"index":19,"text":"值(value): 行的具体信息, 每个值必须与该列的数据类型相同;","id":"9dbe1b04-32d6-4c5d-9dd7-0787115f4182","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-19"},{"bbox":[79,603,246,613],"type":"text","angle":0,"index":20,"text":"键(key): 键的值在当前列中具有唯一性。、","id":"c12f9d20-adc4-418f-b457-6bb5ae84ea56","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"page_size":[595,841],"block_position":"0-20"},{"bbox":[80,629,373,640],"type":"text","angle":0,"index":22,"text":"虽然查找表和视图表在形式上都可以被视为“表”，但它们之间有几个重要的区别：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"3a54b445-2430-4129-a725-1b674dbfa55c","page_size":[595,841],"block_position":"0-21"},{"bbox":[80,655,99,666],"type":"text","angle":0,"index":23,"text":"特性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"2eb82da7-2f94-4c6e-a072-f2e0ecd55909","page_size":[595,841],"block_position":"0-22"},{"bbox":[124,655,186,666],"type":"text","angle":0,"index":24,"text":"查找表（物理表）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"02c37aa1-0b73-4d03-9d5b-f7ad004cbed9","page_size":[595,841],"block_position":"0-23"},{"bbox":[240,655,301,666],"type":"text","angle":0,"index":25,"text":"视图表（虚拟表）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"9c6e0bc2-ba79-4545-9098-f5c70abc2d6a","page_size":[595,841],"block_position":"0-24"},{"bbox":[80,692,115,701],"type":"text","angle":0,"index":26,"text":"数据存储","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"701010b9-f70a-48d9-b086-741c90ad0a2a","page_size":[595,841],"block_position":"0-25"},{"bbox":[124,692,175,701],"type":"text","angle":0,"index":27,"text":"存储实际数据","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"226b7d16-5f54-43c0-b804-b4df6b33c1f0","page_size":[595,841],"block_position":"0-26"},{"bbox":[248,683,354,694],"type":"text","angle":0,"index":28,"text":"不存储数据，只包含查询逻辑","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"a80c7c7d-618e-4a6b-8352-b61153150ecc","page_size":[595,841],"block_position":"0-27"},{"bbox":[240,699,322,709],"type":"text","angle":0,"index":29,"text":"基于查询结果动态生成","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"cfd01e12-2ac0-4aca-808c-44febefe1ca9","page_size":[595,841],"block_position":"0-28"},{"bbox":[80,727,99,736],"type":"text","angle":0,"index":30,"text":"性能","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"ccfae074-20fb-4fa8-806a-76620342c68b","page_size":[595,841],"block_position":"0-29"},{"bbox":[124,727,222,736],"type":"text","angle":0,"index":31,"text":"查询时直接操作存储的数据","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"84a562ca-22e4-497e-a10d-1878d5bb6f49","page_size":[595,841],"block_position":"0-30"},{"bbox":[240,727,401,737],"type":"text","angle":0,"index":32,"text":"查询时动态执行SQL语句，可能会有额外开销","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":0,"id":"8a9292b3-4f6e-4173-b43f-de63fe6d0993","page_size":[595,841],"block_position":"0-31"}],[{"bbox":[80,80,99,91],"type":"header","angle":0,"index":-99999,"text":"特性","color":{"line":"rgba(164, 164, 164, 1)","fill":"rgba(164, 164, 164, 1)"},"page_idx":1,"is_discarded":true,"id":"e31c3ba8-e2ea-4cb8-aae9-bb54947d0fd7","page_size":[595,841],"block_position":"1-0"},{"bbox":[124,80,186,91],"type":"header","angle":0,"index":-99998,"text":"查找表（物理表）","color":{"line":"rgba(164, 164, 164, 1)","fill":"rgba(164, 164, 164, 1)"},"page_idx":1,"is_discarded":true,"id":"79aabe8f-e336-4c86-8971-d9a01fdeaac4","page_size":[595,841],"block_position":"1-1"},{"bbox":[240,80,302,91],"type":"header","angle":0,"index":-99997,"text":"视图表（虚拟表）","color":{"line":"rgba(164, 164, 164, 1)","fill":"rgba(164, 164, 164, 1)"},"page_idx":1,"is_discarded":true,"id":"5dbf35e9-9039-4595-ad8d-5a992206efad","page_size":[595,841],"block_position":"1-2"},{"bbox":[79,108,442,119],"type":"text","angle":0,"index":3,"text":"更新操作 数据可更新，直接修改表中的数据对视图的更新可能会有限制，特别是当视图涉及多个表时","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"5ec3da2b-afbc-431e-ae36-734a153ea490","page_size":[595,841],"block_position":"1-3"},{"bbox":[79,136,207,147],"type":"text","angle":0,"index":4,"text":"复杂查询封装不支持复杂的查询封装","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"aa50d8de-4ab6-4232-948b-cc0d507592a7","page_size":[595,841],"block_position":"1-4"},{"bbox":[239,136,363,147],"type":"text","angle":0,"index":5,"text":"支持复杂查询封装，可以简化访问","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"ba841bca-05a0-4c1a-a262-62cc35124c0f","page_size":[595,841],"block_position":"1-5"},{"bbox":[80,163,167,174],"type":"text","angle":0,"index":6,"text":"查询方式 直接查询表","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"42a7c402-c820-4804-9cac-77f8b2ae447d","page_size":[595,841],"block_position":"1-6"},{"bbox":[239,163,387,174],"type":"text","angle":0,"index":7,"text":"查询视图会间接查询底层表。作为表使用","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"9e150e26-25f3-4b94-b810-b63a5bd55d21","page_size":[595,841],"block_position":"1-7"},{"bbox":[79,190,402,200],"type":"text","angle":0,"index":8,"text":"您可以使用 MySQL 二进制方式进入到 mysql 命令提示符下来连接 MySQL 数据库，格式如下：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"259c3379-cbd4-4d4d-8274-f37c7ded6334","page_size":[595,841],"block_position":"1-8"},{"bbox":[79,216,173,227],"type":"text","angle":0,"index":9,"text":"mysql -u your_username -p","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"3e0df4fe-6393-4e7e-946e-edd40c389db9","page_size":[595,841],"block_position":"1-9"},{"bbox":[87,246,289,267],"type":"title","angle":0,"index":10,"text":"# 数据库技术中的四个名词","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":1,"id":"e68c8cc2-97ed-401c-9f98-b8fdfcf4415f","page_size":[595,841],"block_position":"1-10"},{"bbox":[104,275,391,287],"type":"text","angle":0,"index":11,"text":"DB：数据库（Database),DB 是统一管理的相关数据的集合。","id":"c4276812-293b-486c-9d16-e364084b1934","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-11"},{"bbox":[104,290,505,349],"type":"text","angle":0,"index":12,"text":"DBMS：数据库管理系统（Database Management System)，DBMS 是位于用户与操作系统之间的一层数据管理软件，为用户或应用程序提供访问DB的方法，包括DB的建立、查询、更新及各种数据控制。DBMS总是基于某种数据模型，可以分为层次型、网状型、关系型、面向对象型 DBMS。","id":"44a003a3-f500-420d-b25e-daed1f75eca3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-12"},{"bbox":[104,353,504,396],"type":"text","angle":0,"index":13,"text":"DBS：数据库系统（Database System),DBS是实现有组织地、动态地存储大量关联数据，方便多用户访问的计算机软件、硬件和数据资源组成的系统，即采用了数据库技术的计算机系统。","id":"58f8023e-6673-443c-920d-3d7e19a313e5","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-13"},{"bbox":[104,399,508,444],"type":"text","angle":0,"index":14,"text":"DBA：数据库管理员。是DBS中的一类人员，或者公司的一个岗位名称。是从事管理和维护数据库管理系统(DBMS)的相关工作人员的统称，他属于运维工程师的一个分支，主要负责业务数据库从设计、测试、部署交付到运行监控的全生命周期管理。","id":"d139f9d2-82ec-48d6-9bde-475f1db9a2af","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-14"},{"bbox":[104,446,445,460],"type":"text","angle":0,"index":15,"text":"数据库技术：是一门研究数据库结构、存储、管理和使用的软件学科。","id":"17dfe4cf-d35f-4a3c-aeac-0ebdd5db9ea0","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-15"},{"bbox":[87,468,219,486],"type":"title","angle":0,"index":17,"text":"# DBMS的主要功能:","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":1,"id":"9f79df46-a60d-4e93-a552-04ff4525ca95","page_size":[595,841],"block_position":"1-16"},{"bbox":[95,493,429,506],"type":"text","angle":0,"index":18,"text":"（1）数据库的定义功能 DDL打开SSMS（客户端工具：图形化/SQL语句）","id":"63b4dc07-e462-43e1-8add-fb5c5a7e6f9d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-17"},{"bbox":[95,508,480,522],"type":"text","angle":0,"index":19,"text":"（2）数据库的操纵功能 DML（对数据进行增删改：Insert、delete、Update（更新））","id":"e6971ed1-0bfd-4704-bfee-22ed8e332213","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-18"},{"bbox":[86,524,503,552],"type":"text","angle":0,"index":21,"text":"（3）数据库的保护功能(实现保护的四个子系统）安全性、完整性、并发控制、备份恢复访问控制","id":"c3f67fe9-ab08-46f4-82f7-a9595c1eaa8e","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-19"},{"bbox":[95,555,309,568],"type":"text","angle":0,"index":22,"text":"（4）数据库的存储管理 （物理存储）DBA 工作","id":"1b880f59-098c-464f-be96-d97d67f57439","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-20"},{"bbox":[86,571,508,599],"type":"text","angle":0,"index":23,"text":"（5）数据库的维护功能 （数据字典：DD元数据：数据的数据 Master数据库中的Sys表，系统配置）","id":"521a76c8-8428-4fc2-ad75-3c97a8e96197","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"page_size":[595,841],"block_position":"1-21"},{"bbox":[88,602,108,613],"type":"text","angle":0,"index":25,"text":"DBS","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"d8645530-68dd-411d-9236-f5c0846bf86f","page_size":[595,841],"block_position":"1-22"},{"bbox":[87,618,157,630],"type":"title","angle":0,"index":26,"text":"# 3.1 DBS 的组成","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":1,"id":"ed82dc71-d7bd-46fb-b234-36b2360c6337","page_size":[595,841],"block_position":"1-23"},{"bbox":[86,634,509,661],"type":"text","angle":0,"index":27,"text":"DBS是采用了数据库技术的计算机系统。DBS是一个实际可运行的， 按照数据库方法存储、维护和向应用系统提供数据支持的计算机系统。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"a97e8562-16ab-4a18-92f4-d13c2add9333","page_size":[595,841],"block_position":"1-24"},{"bbox":[86,665,358,677],"type":"text","angle":0,"index":28,"text":"DBS由四部分组成：数据库(DB)、硬件、软件、数据库用户","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"fce78b3d-3de7-492f-90f9-08d383396e92","page_size":[595,841],"block_position":"1-25"},{"bbox":[86,681,375,692],"type":"text","angle":0,"index":29,"text":"数据库用户可分为：DBA，专业用户，专业程序员，最终用户。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"346e9c2b-e045-48fb-8451-6fcd86573748","page_size":[595,841],"block_position":"1-26"},{"bbox":[87,696,186,708],"type":"text","angle":0,"index":30,"text":"(主要理解 DB 和 DBA)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"a916c5a0-88c2-466b-9376-f559d4abd210","page_size":[595,841],"block_position":"1-27"},{"bbox":[86,711,504,740],"type":"text","angle":0,"index":31,"text":"DBA是控制数据整体结构的人，负责DBS的正常运行。DBA可以是一个人，在大型系统中也可以是由几个人组成的小组。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":1,"id":"ef9cf91e-2a0d-4620-b7c8-3b9d8fddd7d9","page_size":[595,841],"block_position":"1-28"}],[{"bbox":[86,95,199,106],"type":"text","angle":0,"index":0,"text":"DBA 的主要职责有五点：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"aef59ebe-87a3-4ed6-9cd2-8f909e42411b","page_size":[595,841],"block_position":"2-0"},{"bbox":[96,110,183,122],"type":"text","angle":0,"index":1,"text":"（1）概念模式定义","id":"a30dc011-5d47-496a-96e4-b9c972bc6965","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-1"},{"bbox":[96,126,172,137],"type":"text","angle":0,"index":2,"text":"（2）内模式定义","id":"717ee80f-f3fe-4e40-89ed-e0760a83c376","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-2"},{"bbox":[96,141,308,153],"type":"text","angle":0,"index":3,"text":"（3）根据要求修改数据库的概念模式和内模式","id":"7a1aae33-33cb-46ce-bd11-6cd8d9ea2534","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-3"},{"bbox":[96,157,214,169],"type":"text","angle":0,"index":4,"text":"（4）对数据库访问的授权","id":"35ec8a45-d181-4e37-989e-8f23b4eb3ed9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-4"},{"bbox":[96,173,204,185],"type":"text","angle":0,"index":5,"text":"（5）完整性约束的说明","id":"ebbf0b9b-834c-4e33-bb41-b3fadab66c9e","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-5"},{"bbox":[91,188,238,200],"type":"title","angle":0,"index":7,"text":"# 4.1 数据库应用软件结构的发展","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":2,"id":"6dd0a97f-9343-4ffc-9d91-37fe60a45572","page_size":[595,841],"block_position":"2-6"},{"bbox":[86,203,504,232],"type":"text","angle":0,"index":8,"text":"从单用户、Client/Server 模式（局域网）、Browser/Server 模式（互联网）、C/S 和 B/S 混合结构","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"e681fbf8-bf47-4ab5-aae9-2de2829505ed","page_size":[595,841],"block_position":"2-7"},{"bbox":[87,250,121,261],"type":"text","angle":0,"index":9,"text":"4.2 C/S","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"7e724a15-5e08-4d36-959a-bfb6d52e7d0b","page_size":[595,841],"block_position":"2-8"},{"bbox":[86,265,498,295],"type":"text","angle":0,"index":10,"text":"C/S是将需要处理的业务合理地分配到客户端和服务器端，这样可以大大降低通信成本，但是升级维护相对困难。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"65325ea1-5e79-4983-a2cf-6df3abe3897e","page_size":[595,841],"block_position":"2-9"},{"bbox":[88,297,230,310],"type":"text","angle":0,"index":11,"text":"了解客户端和服务器端的分工。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"33e0544f-36cf-4cd8-ae09-053e9b38b5c0","page_size":[595,841],"block_position":"2-10"},{"bbox":[87,328,121,338],"type":"text","angle":0,"index":12,"text":"4.3 B/S","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"42407916-8346-4846-9601-419e87eda9b9","page_size":[595,841],"block_position":"2-11"},{"bbox":[86,343,509,388],"type":"text","angle":0,"index":13,"text":"B/S结构是随着互联网的发展，web出现后兴起的一种网络结构模式。这种模式统一了客户端，让核心的业务处理在服务端完成。B/S维护和升级方式更简单。由于客户端是浏览器，基本不需要维护，只需要维护升级服务器端。但安全性上不如C/S可控。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"19d42755-ce52-455d-9132-417811e81a9d","page_size":[595,841],"block_position":"2-12"},{"bbox":[87,406,174,418],"type":"title","angle":0,"index":14,"text":"# 数据库的体系结构","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":2,"id":"4f1347b8-e5a8-4977-ae07-88d68501f090","page_size":[595,841],"block_position":"2-13"},{"bbox":[87,422,169,434],"type":"title","angle":0,"index":15,"text":"# 5.1 三级模式结构","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":2,"id":"928e3373-4c52-4de9-b32e-1c587f638522","page_size":[595,841],"block_position":"2-14"},{"bbox":[87,437,336,450],"type":"text","angle":0,"index":16,"text":"三级模式、二级映像的目的：为了提高数据的独立性。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"79a2d276-8754-4e11-99af-63f39e8b6b60","page_size":[595,841],"block_position":"2-15"},{"bbox":[86,453,446,465],"type":"text","angle":0,"index":17,"text":"数据库的体系结构分为三级：内部级、概念级和外部级(数据抽象的三个级别）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"167df633-d6b8-4fcf-b2b8-4f5d3e7b1f80","page_size":[595,841],"block_position":"2-16"},{"bbox":[87,469,286,481],"type":"text","angle":0,"index":18,"text":"(1)外部级：单个用户所能看到的数据特性；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"04de959f-968c-48ca-a393-2b7fea4ebaa2","page_size":[595,841],"block_position":"2-17"},{"bbox":[91,483,467,497],"type":"text","angle":0,"index":19,"text":"单个用户使用的数据视图的描述称“外模式”，又称“子模式”。（最接近用户）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"73820cce-049e-4f71-81ba-b75fe22f8f86","page_size":[595,841],"block_position":"2-18"},{"bbox":[87,500,369,513],"type":"text","angle":0,"index":20,"text":"(2)概念级：涉及到所有用户的数据定义，是全局的数据视图；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"2f702c58-d324-490d-820f-62df9e191d26","page_size":[595,841],"block_position":"2-19"},{"bbox":[91,515,341,528],"type":"text","angle":0,"index":21,"text":"全局数据视图的描述称“概念模式”，又称“模式”。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"d4930d75-c60c-4583-97e8-97f27f85b950","page_size":[595,841],"block_position":"2-20"},{"bbox":[87,531,368,544],"type":"text","angle":0,"index":22,"text":"(3)内部级：最接近于物理存储，涉及到实际数据存储的结构；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"4a8ec95b-168c-49bf-88a0-9cc53f1ce70e","page_size":[595,841],"block_position":"2-21"},{"bbox":[91,546,268,559],"type":"text","angle":0,"index":23,"text":"物理存储视图的描述称为“内模式”。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"101269f4-13ba-4ae1-abc4-fc8ed0f9016b","page_size":[595,841],"block_position":"2-22"},{"bbox":[87,562,339,575],"type":"text","angle":0,"index":24,"text":"(进一步理解三级模式的具体含义，并掌握两个映象。)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"1b27f59d-0a56-4a03-8009-6d99689d633a","page_size":[595,841],"block_position":"2-23"},{"bbox":[86,577,505,621],"type":"text","angle":0,"index":25,"text":"数据按外模式的描述提供给用户（应用程序），按内模式的描述存储在磁盘中， 而概念模式提供了连接这两级的相对稳定的中间观点，并使得任何一级的改变都不受另一级的牵制。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"088679e8-0d84-4d8d-99b7-a141cda020d4","page_size":[595,841],"block_position":"2-24"},{"bbox":[87,624,306,637],"type":"text","angle":0,"index":26,"text":"(1)概念模式 （模式）：具体含义；（模式 DDL）","id":"29b9d4c2-3012-4f87-8629-667d1b9e4da5","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-25"},{"bbox":[87,640,262,652],"type":"text","angle":0,"index":27,"text":"(2)外模式：具体含义；（外模式 DDL）","id":"24cc0b3d-0b87-475c-86fa-dcd00000579b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-26"},{"bbox":[98,655,431,668],"type":"text","angle":0,"index":29,"text":"外模式又称为“用户模式”或“子模式”，通常是概念模式的逻辑子集。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"564bdf64-8a8d-4ccc-94a5-eef9969e7094","page_size":[595,841],"block_position":"2-27"},{"bbox":[87,671,262,684],"type":"text","angle":0,"index":30,"text":"(3)内模式：具体含义；（内模式 DDL）","id":"25574137-00d3-46ad-a94e-c203de562f1d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-28"},{"bbox":[86,687,497,715],"type":"text","angle":0,"index":31,"text":"(4)模式/内模式映象：用于定义概念模式和内模式之间的对应性。一般在内模式中描述。保证数据的物理独立性。","id":"0678680b-a2c2-402a-8a06-6f5dc67231b2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-29"},{"bbox":[87,718,456,730],"type":"text","angle":0,"index":32,"text":"(5)外模式/模式映象：用于定义外模式和概念模式间的对应性。在外模式中描述。","id":"1eda5be5-cbbf-4f2d-abbf-fe5b369b9a70","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"page_size":[595,841],"block_position":"2-30"},{"bbox":[87,734,195,746],"type":"text","angle":0,"index":34,"text":"保证数据的逻辑独立性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"1bad1719-8605-4c34-b3c1-3fc67a9ce0ca","page_size":[595,841],"block_position":"2-31"},{"bbox":[86,749,504,761],"type":"text","angle":0,"index":35,"text":"(1) 物理数据独立性：修改内模式时尽量不影响概念模式及外模式，从而达到不影响既有应","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":2,"id":"456946a6-69ba-4989-ad2b-d908e58c9bb1","page_size":[595,841],"block_position":"2-32"}],[{"bbox":[86,79,157,91],"type":"text","angle":0,"index":0,"text":"用程序的目的。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"b2487661-c329-41be-bcf2-0b984473cadc","page_size":[595,841],"block_position":"3-0"},{"bbox":[86,95,504,122],"type":"text","angle":0,"index":1,"text":"(2) 逻辑数据独立性：修改概念模式时尽量不影响外模式和应用程序，从而达到不影响既有应用程序的目的。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"2d830281-0521-4150-8b68-79aee0a00922","page_size":[595,841],"block_position":"3-1"},{"bbox":[87,125,227,138],"type":"text","angle":0,"index":2,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"0875a8fe-602c-4aa3-bdb2-b3a5677f2cf5","page_size":[595,841],"block_position":"3-2"},{"bbox":[86,142,227,154],"type":"text","angle":0,"index":3,"text":"知识点：主要是一些基本概念","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"57dc7cee-0060-48c1-a115-1bdfdecd0ce1","page_size":[595,841],"block_position":"3-3"},{"bbox":[86,172,290,185],"type":"text","angle":0,"index":4,"text":"三个世界：现实世界、信息世界、数据世界","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"0a00a953-2084-47c4-9c04-3a568ab6cf11","page_size":[595,841],"block_position":"3-4"},{"bbox":[86,188,383,201],"type":"text","angle":0,"index":5,"text":"对应模型：信息世界：概念模型（ER 图或者 UML 表达概念模型）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"6b94c92c-0ea7-41a4-bac2-53be5a696894","page_size":[595,841],"block_position":"3-5"},{"bbox":[86,203,504,232],"type":"text","angle":0,"index":6,"text":"数据世界：先设计出逻辑模型再转化为物理模型（我们只讨论关系数据模型，其他模型只需大致了解）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"beca1ca7-03d5-47a6-a2bf-744892b303dc","page_size":[595,841],"block_position":"3-6"},{"bbox":[86,235,282,248],"type":"text","angle":0,"index":7,"text":"对应概念： 对象- 实体 -元组（记录）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"9aa58db4-8308-4669-b939-7d5b5f2dbb33","page_size":[595,841],"block_position":"3-7"},{"bbox":[111,250,265,263],"type":"text","angle":0,"index":8,"text":"一类对象—>实体集—>关系（表）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"2ae7a58d-e570-475d-8a55-eaa6999092d4","page_size":[595,841],"block_position":"3-8"},{"bbox":[120,265,217,279],"type":"text","angle":0,"index":9,"text":"特性—>属性 属性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"7e11b7bf-70c6-4a02-9393-4a50744364cb","page_size":[595,841],"block_position":"3-9"},{"bbox":[139,281,183,294],"type":"text","angle":0,"index":10,"text":"域  域","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"7ae30b6d-b9c0-4068-a652-07144222765a","page_size":[595,841],"block_position":"3-10"},{"bbox":[139,296,260,310],"type":"text","angle":0,"index":11,"text":"码  码（候选码、主码）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"3136733f-80dc-48c7-ab24-70ef824cdecb","page_size":[595,841],"block_position":"3-11"},{"bbox":[111,312,408,326],"type":"text","angle":0,"index":12,"text":"对象间的联系—》实体集间的联系—》属性、关系（表），外码","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"7fb61852-9c22-414e-ab26-22a9e44dda6a","page_size":[595,841],"block_position":"3-12"},{"bbox":[86,328,309,341],"type":"text","angle":0,"index":13,"text":"采用ER方法进行数据库概念设计分成三步进行：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"63aa93bf-2c8d-4a90-9ff2-0a3fd3006553","page_size":[595,841],"block_position":"3-13"},{"bbox":[86,343,258,356],"type":"text","angle":0,"index":14,"text":"实体、属性、实体集、联系、域、码","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"74a46909-008c-41a5-ad00-a6721a10b176","page_size":[595,841],"block_position":"3-14"},{"bbox":[86,359,342,372],"type":"text","angle":0,"index":15,"text":"联系的类型（阶）：1：1、1：N（或者 N：1）、M：N","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"ea0b1187-565c-4b9b-b5b3-2ea96b15a29d","page_size":[595,841],"block_position":"3-15"},{"bbox":[87,406,180,418],"type":"text","angle":0,"index":16,"text":"(1)设计局部 ER 模式","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"e6ff24cc-ca6d-494a-9822-550ed608c831","page_size":[595,841],"block_position":"3-16"},{"bbox":[96,422,341,434],"type":"text","angle":0,"index":17,"text":"确定局部结构范围；实体定义；联系定义；属性分配","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"95902e7c-2ded-4897-a41f-a55d0bc6ca49","page_size":[595,841],"block_position":"3-17"},{"bbox":[88,438,180,449],"type":"text","angle":0,"index":18,"text":"(2)设计全局ER模式","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"ce2441f8-0720-4c20-8151-4f197f40cdd3","page_size":[595,841],"block_position":"3-18"},{"bbox":[96,453,335,465],"type":"text","angle":0,"index":19,"text":"确定公共实体类型；局部ER模型的合并；消除冲突","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"612b1a1a-75ba-4305-a096-8c2f0d7ae010","page_size":[595,841],"block_position":"3-19"},{"bbox":[88,469,201,481],"type":"text","angle":0,"index":20,"text":"(3)全局ER模式进行优化","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"2631e04e-d655-4a06-a815-aec9ee732f8c","page_size":[595,841],"block_position":"3-20"},{"bbox":[96,484,341,497],"type":"text","angle":0,"index":21,"text":"实体类型的合并；冗余属性的消除；冗余联系的消除","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"f5543eee-6ead-4246-916c-a8dee8fd55eb","page_size":[595,841],"block_position":"3-21"},{"bbox":[87,500,352,512],"type":"text","angle":0,"index":22,"text":"(1) 二维表格 在关系模型中，一张二维表格对应一个关系。","id":"805d0d96-e502-4420-828e-61a59f122f3a","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"page_size":[595,841],"block_position":"3-22"},{"bbox":[87,515,436,528],"type":"text","angle":0,"index":23,"text":"(2) 元组 表中的一行（即一个记录），表示一个实体；关系是由元组组成的。","id":"d38a9e51-c058-4220-a38f-8ddf72b28ed9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"page_size":[595,841],"block_position":"3-23"},{"bbox":[88,531,383,543],"type":"text","angle":0,"index":24,"text":"(3) 域 是一组具有相同数据类型的值的集合。（属性的取值范围）","id":"a7b3b9cf-52cd-4037-8ef0-3799022bd066","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"page_size":[595,841],"block_position":"3-24"},{"bbox":[88,546,247,559],"type":"text","angle":0,"index":25,"text":"(4) 笛卡尔积域上的一种集合运算。","id":"56fd33ed-25cc-4d00-abf0-5c4f76755e1b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"page_size":[595,841],"block_position":"3-25"},{"bbox":[86,562,504,590],"type":"text","angle":0,"index":26,"text":"(5) 关系：是一个元数为 $\\mathsf { K } ( \\mathsf { K } > = 1 )$ 的元组的集合。 一张二维表格对应一个关系。表中的一行称为关系的一个元组；表中的一列称为关系的一个属性。","id":"b6c938b2-de94-49e6-a1a3-f63d8968c7c7","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"page_size":[595,841],"block_position":"3-26"},{"bbox":[86,593,420,606],"type":"text","angle":0,"index":28,"text":"在关系模型中，对关系作了下列规范性的限制：（关系的六条基本性质）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"ef80b495-9672-4e41-9965-3f3657f13dc6","page_size":[595,841],"block_position":"3-27"},{"bbox":[99,616,276,629],"type":"text","angle":0,"index":29,"text":"关系中每一个属性值都是不可分解的；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"6369ffbb-cb2b-4cf2-9ac5-c2def8ef01a2","page_size":[595,841],"block_position":"3-28"},{"bbox":[99,631,321,645],"type":"text","angle":0,"index":30,"text":"关系中不允许出现相同的元组（没有重复元组)；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"8551f019-6a20-465b-9215-a8acf8b2e8f6","page_size":[595,841],"block_position":"3-29"},{"bbox":[99,648,265,661],"type":"text","angle":0,"index":31,"text":"不考虑元组间的顺序，即没有行序；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"f13e341c-a069-4246-a5ae-b58845d8643d","page_size":[595,841],"block_position":"3-30"},{"bbox":[99,663,339,676],"type":"text","angle":0,"index":32,"text":"在理论上，属性间的顺序（即列序）也是不存在的；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"7c332805-df59-48c9-8861-f956a287387b","page_size":[595,841],"block_position":"3-31"},{"bbox":[99,678,411,691],"type":"text","angle":0,"index":33,"text":"列是同质的，即每一列中的分量是同一类型的数据，来自同一个域；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"f222342a-0b66-4044-abb3-c5811dd9e236","page_size":[595,841],"block_position":"3-32"},{"bbox":[99,694,380,707],"type":"text","angle":0,"index":34,"text":"不同的列可出自同一个域，不同的属性要给予不同的属性名。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"b0aa1431-ea7d-4f3a-9b28-ae45d3b970e9","page_size":[595,841],"block_position":"3-33"},{"bbox":[89,717,458,730],"type":"text","angle":0,"index":35,"text":"(6) 超码 （Super Key） ： 在关系中能唯一标识元组的属性集称为关系模式的超码；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"25bdcbc0-29e6-4a43-ac53-9cc9dafe57b0","page_size":[595,841],"block_position":"3-34"},{"bbox":[87,732,504,761],"type":"text","angle":0,"index":36,"text":"(7) 候选码(Candidate Key)：不含有多余属性的超码称为候选码； 关系中能唯一地标识一个元组而不包含多余属性的属性（或属性组），叫码或者候选码，一个关系可以有多个候选","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":3,"id":"2d184437-4de7-4bff-8b57-b02e9cdf79d0","page_size":[595,841],"block_position":"3-35"}],[{"bbox":[86,79,104,90],"type":"text","angle":0,"index":0,"text":"码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"b3921df9-1325-469e-9cf3-b1408ed46a9c","page_size":[595,841],"block_position":"4-0"},{"bbox":[86,94,509,122],"type":"text","angle":0,"index":1,"text":"(8) 主码（Primary Key）：用户选作元组标识的一个候选码。 如果一个关系有多个候选码，则选择其中一个作为主码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"1fa75b3e-9303-48b3-a83a-7a521cfcc328","page_size":[595,841],"block_position":"4-1"},{"bbox":[86,125,452,138],"type":"text","angle":0,"index":2,"text":"在以上概念中，主码一定可作候选码，候选码一定可作超码；反之，则不成立。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"64a957e3-dd97-42fa-8440-0dc132b4f80d","page_size":[595,841],"block_position":"4-2"},{"bbox":[86,141,503,216],"type":"text","angle":0,"index":3,"text":"比如，在学生表中，如果有“学号”、“姓名”、“出生年月”等字段， 其中学号是唯一的，那么（学号）属于超码，（学号，姓名）的组合也是超码。 同时，（学号）是候选码而（学号，姓名）由于含有多余属性，所以不是候选码。 在这三个概念中，主码的概念最为重要，它是用户选作元组标识的一个关键字。 如果一个关系中有两个或两个以上候选码用户就选其中之一作为主码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"0e3c09eb-ef7a-406c-8750-d5a8bb11f3c9","page_size":[595,841],"block_position":"4-3"},{"bbox":[86,219,504,262],"type":"text","angle":0,"index":4,"text":"(1) 实体完整性规则 要求关系中元组在组成候选码的属性上不能有空值。如果出现空值，那么候选码就起不了唯一标识元组的作用。（对关系的码的约束） 主码 Primary key 也叫主键","id":"cb1075ea-cacd-4bca-9995-849820ecc06e","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-4"},{"bbox":[86,265,498,294],"type":"text","angle":0,"index":5,"text":"(2) 参照完整性规则 要求外码值必须是（另）一个关系的主码的有效值，或者是空值。（对关系外码的约束）","id":"27b60b61-6661-47ce-b9c3-1fd7b919d5a6","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-5"},{"bbox":[99,304,508,333],"type":"text","angle":0,"index":7,"text":"外码：（Foreign Key 也叫外键）将一个关系的主码（比如 学生关系 S 中的 S#） 放到另一个关系（比如选课关系SC）中，此时称Sno是关系SC的外码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"322f1697-1b0f-4e1a-84dd-f6eded8ca27e","page_size":[595,841],"block_position":"4-6"},{"bbox":[99,351,149,364],"type":"text","angle":0,"index":8,"text":"注意事项：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"2f6aefb1-62d1-4ac4-9d0e-2e6715a326c2","page_size":[595,841],"block_position":"4-7"},{"bbox":[99,366,380,380],"type":"text","angle":0,"index":9,"text":"外码和相应的主码可以不同名，只要定义在相同值域上即可；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"fff4b918-89d1-43df-891b-8ec0cdf459bf","page_size":[595,841],"block_position":"4-8"},{"bbox":[99,382,369,395],"type":"text","angle":0,"index":10,"text":"两个关系可以是同一个关系模式，表示了属性之间的联系。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"2b52b352-32bc-4c4c-a574-9f9bf9af6a5c","page_size":[595,841],"block_position":"4-9"},{"bbox":[99,398,281,411],"type":"text","angle":0,"index":11,"text":"外码值是否允许空，应视具体情况而定","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"a715ae09-db13-44ad-9d71-ea7c6bc63bf9","page_size":[595,841],"block_position":"4-10"},{"bbox":[86,421,508,465],"type":"text","angle":0,"index":12,"text":"(3) 用户定义的完整性规则：这是针对某一具体数据的约束条件，由应用环境决定， 例如，学生的年龄限制为15~30周岁。 用户定义的完整性规则反映某一具体应用涉及的数据必须满足的语义要求。 系统提供定义和检验这类完整性的机制。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"b93e1955-5257-430c-bf7b-d80cb0b7f6c4","page_size":[595,841],"block_position":"4-11"},{"bbox":[86,471,265,484],"type":"title","angle":0,"index":13,"text":"# 3 数据模型和关系数据模型的基本概念","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":4,"id":"1bebdfe8-09a4-48c2-8397-954e095935de","page_size":[595,841],"block_position":"4-12"},{"bbox":[87,487,180,499],"type":"title","angle":0,"index":14,"text":"# 3.1 数据模型三要素","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":4,"id":"b2df5d65-0e46-4d30-8b70-8e7a6ea044aa","page_size":[595,841],"block_position":"4-13"},{"bbox":[87,502,227,515],"type":"text","angle":0,"index":15,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"a9d15875-5ace-4257-ad7d-1a0681531b96","page_size":[595,841],"block_position":"4-14"},{"bbox":[87,518,289,531],"type":"text","angle":0,"index":16,"text":"知识点：数据结构、数据操作、完整性约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"58a19439-d64c-4d79-8f7c-f4dc37ec3c9e","page_size":[595,841],"block_position":"4-15"},{"bbox":[88,534,250,547],"type":"text","angle":0,"index":17,"text":"结合下面的关系数据模型进行理解","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"b6563e88-8563-4689-9e85-87875b224da4","page_size":[595,841],"block_position":"4-16"},{"bbox":[87,565,201,577],"type":"title","angle":0,"index":18,"text":"# 3.2 二维表格的基本术语","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":4,"id":"3e24fea9-4bad-4315-9032-f139271e7586","page_size":[595,841],"block_position":"4-17"},{"bbox":[87,580,227,593],"type":"text","angle":0,"index":19,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"e088d1b6-0ca1-4663-b1b7-a0a31be18234","page_size":[595,841],"block_position":"4-18"},{"bbox":[87,596,227,608],"type":"text","angle":0,"index":20,"text":"知识点：主要是一些基本概念","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"7f6580eb-dbb8-46c4-b202-4ce97fc7844a","page_size":[595,841],"block_position":"4-19"},{"bbox":[86,627,352,640],"type":"text","angle":0,"index":21,"text":"(1) 二维表格 在关系模型中，一张二维表格对应一个关系。","id":"1746100f-6b4c-4ebc-9410-5ad02377e955","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-20"},{"bbox":[86,643,436,655],"type":"text","angle":0,"index":22,"text":"(2) 元组 表中的一行（即一个记录），表示一个实体；关系是由元组组成的。","id":"4778a339-d794-409e-b646-ec417c6723e9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-21"},{"bbox":[86,659,383,671],"type":"text","angle":0,"index":23,"text":"(3) 域 是一组具有相同数据类型的值的集合。（属性的取值范围）","id":"4c045488-ac95-4818-ad22-fc52cbf30006","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-22"},{"bbox":[87,674,247,687],"type":"text","angle":0,"index":24,"text":"(4) 笛卡尔积域上的一种集合运算。","id":"8995d1b2-9f7a-4895-8da5-00ef6b9369ce","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-23"},{"bbox":[86,690,496,718],"type":"text","angle":0,"index":25,"text":"(5) 关系：是一个元数为 $\\mathsf { K } ( \\mathsf { K } > = 1 )$ 的元组的集合。 一张二维表格对应一个关系。表中的一行称为关系的一个元组；表中的一列称为关系的一个属性。","id":"aef3fca6-ef14-4131-ba51-357aff404e20","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"page_size":[595,841],"block_position":"4-24"},{"bbox":[86,721,419,734],"type":"text","angle":0,"index":27,"text":"在关系模型中，对关系作了下列规范性的限制：（关系的六条基本性质）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":4,"id":"d63c244d-a488-4163-9743-7446f75cc1c2","page_size":[595,841],"block_position":"4-25"}],[{"bbox":[101,89,278,104],"type":"text","angle":0,"index":0,"text":"关系中每一个属性值都是不可分解的；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"a8ca3569-588a-42dd-9bb5-ef5ae409e358","page_size":[595,841],"block_position":"5-0"},{"bbox":[101,105,323,119],"type":"text","angle":0,"index":1,"text":"关系中不允许出现相同的元组（没有重复元组)；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"d07fae9b-ae8f-449b-961f-3f04215c9cdd","page_size":[595,841],"block_position":"5-1"},{"bbox":[101,121,268,134],"type":"text","angle":0,"index":2,"text":"不考虑元组间的顺序，即没有行序；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"4441c03f-bb83-4a7d-865b-0a3296dfb5ee","page_size":[595,841],"block_position":"5-2"},{"bbox":[101,137,341,150],"type":"text","angle":0,"index":3,"text":"在理论上，属性间的顺序（即列序）也是不存在的；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"6e1f4f36-5591-468d-baa3-a3c224e9c8be","page_size":[595,841],"block_position":"5-3"},{"bbox":[101,152,414,166],"type":"text","angle":0,"index":4,"text":"列是同质的，即每一列中的分量是同一类型的数据，来自同一个域；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"e7c348db-8435-4466-b020-ffecaa08b675","page_size":[595,841],"block_position":"5-4"},{"bbox":[101,168,382,181],"type":"text","angle":0,"index":5,"text":"不同的列可出自同一个域，不同的属性要给予不同的属性名。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"63625704-1aab-4a1a-b54f-16d4a76ce87b","page_size":[595,841],"block_position":"5-5"},{"bbox":[89,191,459,205],"type":"text","angle":0,"index":6,"text":"(6) 超码 （Super Key） ： 在关系中能唯一标识元组的属性集称为关系模式的超码；","id":"5929fb92-e33d-4c3f-80ed-7dd96297dcee","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"page_size":[595,841],"block_position":"5-6"},{"bbox":[86,206,498,251],"type":"text","angle":0,"index":7,"text":"(7) 候选码(Candidate Key)：不含有多余属性的超码称为候选码； 关系中能唯一地标识一个元组而不包含多余属性的属性（或属性组），叫码或者候选码，一个关系可以有多个候选码。","id":"8900e3fc-1ff8-4b17-ad5a-a0c03fa40b7d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"page_size":[595,841],"block_position":"5-7"},{"bbox":[86,253,498,282],"type":"text","angle":0,"index":8,"text":"(8) 主码（Primary Key）：用户选作元组标识的一个候选码。 如果一个关系有多个候选码，则选择其中一个作为主码。","id":"fcb35a16-806d-428d-ae0c-b868ad21b661","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"page_size":[595,841],"block_position":"5-8"},{"bbox":[86,285,452,298],"type":"text","angle":0,"index":10,"text":"在以上概念中，主码一定可作候选码，候选码一定可作超码；反之，则不成立。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"b59a3887-1906-4c78-bc78-0154a30b579b","page_size":[595,841],"block_position":"5-9"},{"bbox":[93,306,499,384],"type":"text","angle":0,"index":11,"text":"比如，在学生表中，如果有“学号”、“姓名”、“出生年月”等字段， 其中学号是唯一的，那么（学号）属于超码，（学号，姓名）的组合也是超码。 同时，（学号）是候选码，而（学号，姓名）由于含有多余属性，所以不是候选码。 在这三个概念中，主码的概念最为重要，它是用户选作元组标识的一个关键字。 如果一个关系中有两个或两个以上候选码，用户就选其中之一作为主码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"1b619e84-ceb1-476f-aca1-b86fc5a8367e","page_size":[595,841],"block_position":"5-10"},{"bbox":[87,392,201,406],"type":"title","angle":0,"index":12,"text":"# 3.3 关系模型的形式定义","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":5,"id":"62ee18b7-7a62-4104-9ae8-6ee36141f8df","page_size":[595,841],"block_position":"5-11"},{"bbox":[87,408,227,422],"type":"text","angle":0,"index":13,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"f8f20638-132f-4044-9585-3f63fe682b47","page_size":[595,841],"block_position":"5-12"},{"bbox":[87,424,227,438],"type":"text","angle":0,"index":14,"text":"知识点：三个组成部分的了解","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"250bb873-10aa-4b67-91d3-47429612a794","page_size":[595,841],"block_position":"5-13"},{"bbox":[86,455,394,469],"type":"text","angle":0,"index":15,"text":"关系模型有三个组成部分：数据结构、数据操作和完整性约束条件","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"ff49d59f-8f22-4c33-b0b1-9b76ad58c410","page_size":[595,841],"block_position":"5-14"},{"bbox":[87,470,232,484],"type":"text","angle":0,"index":16,"text":"关系模型的的数据结构是关系；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"d66d95d0-a41a-4b34-bb12-68eaf82ced3f","page_size":[595,841],"block_position":"5-15"},{"bbox":[86,486,498,516],"type":"text","angle":0,"index":17,"text":"关系模型提供一组完备的高级关系运算（关系代数 $^ +$ 关系演算），支持数据库的各种操作；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"a7767222-e607-4bd8-af08-a185b790c075","page_size":[595,841],"block_position":"5-16"},{"bbox":[87,518,230,530],"type":"text","angle":0,"index":18,"text":"关系模型包括三类完整性规则。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"1388c2db-4091-44ce-9688-3dc9860c5da5","page_size":[595,841],"block_position":"5-17"},{"bbox":[87,549,232,562],"type":"title","angle":0,"index":19,"text":"# 3.4 关系模型的三类完整性规则","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":5,"id":"5870cafc-df2e-4752-819f-4f53aba960b4","page_size":[595,841],"block_position":"5-18"},{"bbox":[86,564,430,577],"type":"text","angle":0,"index":20,"text":"考核要求：达到“领会”层次，第四章后达到熟悉掌握，是课程重点之一。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"f02eb1e6-bb48-48ed-ad8b-c0f4117e94eb","page_size":[595,841],"block_position":"5-19"},{"bbox":[87,580,237,592],"type":"text","angle":0,"index":21,"text":"知识点：三类完整性规则的理解","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"2f700f9b-0dfd-4794-bb77-7474a1a2b2f1","page_size":[595,841],"block_position":"5-20"},{"bbox":[86,611,498,655],"type":"text","angle":0,"index":22,"text":"(1) 实体完整性规则 要求关系中元组在组成候选码的属性上不能有空值。如果出现空值，那么候选码就起不了唯一标识元组的作用。（对关系的码的约束） 主码 Primary key 也叫主键","id":"4f7d1752-4711-4263-83c1-e532c602893c","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"page_size":[595,841],"block_position":"5-21"},{"bbox":[87,657,492,687],"type":"text","angle":0,"index":23,"text":"(2) 参照完整性规则 要求外码值必须是（另）一个关系的主码的有效值，或者是空值。（对关系外码的约束）","id":"de623887-8029-4f2b-8a11-3a5790844c4d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"page_size":[595,841],"block_position":"5-22"},{"bbox":[101,696,498,726],"type":"text","angle":0,"index":25,"text":"外码：（Foreign Key也叫外键）将一个关系的主码（比如 学生关系S中的S#） 放到另一个关系（比如选课关系SC）中，此时称Sno是关系SC的外码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":5,"id":"17c89027-8d29-48eb-926f-6b9831c31876","page_size":[595,841],"block_position":"5-23"}],[{"bbox":[102,105,151,118],"type":"text","angle":0,"index":0,"text":"注意事项：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"8cc527b5-a0cc-4069-b86e-1d091c6fc61d","page_size":[595,841],"block_position":"6-0"},{"bbox":[102,121,382,135],"type":"text","angle":0,"index":1,"text":"外码和相应的主码可以不同名，只要定义在相同值域上即可；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"96428bd9-f00f-4511-8ad5-7877dcbaf505","page_size":[595,841],"block_position":"6-1"},{"bbox":[102,137,371,150],"type":"text","angle":0,"index":2,"text":"两个关系可以是同一个关系模式，表示了属性之间的联系。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"66b20841-f1b6-448d-b1e8-5a602201e88c","page_size":[595,841],"block_position":"6-2"},{"bbox":[102,153,284,166],"type":"text","angle":0,"index":3,"text":"外码值是否允许空，应视具体情况而定","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"aaeab636-de4f-4e4b-bb13-5f2b528999f8","page_size":[595,841],"block_position":"6-3"},{"bbox":[102,183,214,195],"type":"text","angle":0,"index":4,"text":"假设数据库有如下关系：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"0bcd16d6-8997-40ed-bce7-0bfaedf1d5ee","page_size":[595,841],"block_position":"6-4"},{"bbox":[102,199,269,211],"type":"text","angle":0,"index":5,"text":"学生关系 S (S#、SNAME、AGE、SEX)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"c8ab8d8e-ff63-43c1-87f2-e844c39140d2","page_size":[595,841],"block_position":"6-5"},{"bbox":[102,214,273,227],"type":"text","angle":0,"index":6,"text":"课程关系 C（C#、CNAME、TEACHER）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"e20bed0c-c33e-43ce-a15a-7cd0c2b515f2","page_size":[595,841],"block_position":"6-6"},{"bbox":[102,230,246,243],"type":"text","angle":0,"index":7,"text":"学习关系 SC（S#、C#、GRADE）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"4ee44948-5f74-42ad-b4d2-ac3cd07cf701","page_size":[595,841],"block_position":"6-7"},{"bbox":[102,245,126,258],"type":"text","angle":0,"index":8,"text":"那么","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"e822a1ba-a250-418d-ae71-212f40b432e1","page_size":[595,841],"block_position":"6-8"},{"bbox":[102,260,422,274],"type":"text","angle":0,"index":9,"text":"(1)S#是关系S的主码，因此在关系S中不能为空；（实体完整性规则）","id":"72fc6fdc-6a1d-4975-a602-b416a31ca54d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"page_size":[595,841],"block_position":"6-9"},{"bbox":[102,276,424,290],"type":"text","angle":0,"index":10,"text":"(2)C#是关系C的主码，因此在关系C中不能为空；（实体完整性规则）","id":"de63a028-24d6-4583-a27b-9eca0aa341c9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"page_size":[595,841],"block_position":"6-10"},{"bbox":[102,292,155,304],"type":"text","angle":0,"index":12,"text":"关系SC中：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"79204c7a-9caa-4c95-b56b-6d7205b2101c","page_size":[595,841],"block_position":"6-11"},{"bbox":[110,307,457,321],"type":"text","angle":0,"index":13,"text":"（S#，C#）的组合为主码，因此S#、C#各自都不能为空；（实体完整性规则）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"da6de870-097f-48bb-a10e-84402c69f784","page_size":[595,841],"block_position":"6-12"},{"bbox":[102,323,474,352],"type":"text","angle":0,"index":14,"text":"S#是来自S的外码，因此它必须和关系S中某个元组的S#相同。（参照完整性规则）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"9647f80f-c0e1-4ecb-ad98-e47b01939013","page_size":[595,841],"block_position":"6-13"},{"bbox":[101,354,474,383],"type":"text","angle":0,"index":15,"text":"C#是来自C的外码，因此它必须和关系C中某个元组的C#相同。（参照完整性规则）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"285fc4ef-ae83-4772-99d8-1d4ead9d3319","page_size":[595,841],"block_position":"6-14"},{"bbox":[86,392,498,439],"type":"text","angle":0,"index":16,"text":"(3) 用户定义的完整性规则：这是针对某一具体数据的约束条件，由应用环境决定， 例如，学生的年龄限制为 15~30 周岁。 用户定义的完整性规则反映某一具体应用涉及的数据必须满足的语义要求。 系统提供定义和检验这类完整性的机制。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"376241fd-4549-463e-9e24-aecba020c2e1","page_size":[595,841],"block_position":"6-15"},{"bbox":[86,454,358,469],"type":"title","angle":0,"index":17,"text":"# 4 概念模型向关系数据模型的转化（即 ER 图转化为表结构）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":6,"id":"b61920e6-5e7e-4df4-a947-a6cf6315470f","page_size":[595,841],"block_position":"6-16"},{"bbox":[86,470,248,484],"type":"text","angle":0,"index":18,"text":"考核要求：达到“熟练掌握”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"8c7a0858-bbee-4438-a5f0-a9d5c7d456b2","page_size":[595,841],"block_position":"6-17"},{"bbox":[86,486,206,499],"type":"text","angle":0,"index":19,"text":"知识点：转换的实际操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"20d98ea4-99c9-417f-975c-0183c8258b34","page_size":[595,841],"block_position":"6-18"},{"bbox":[86,502,257,515],"type":"text","angle":0,"index":20,"text":"ER模型转换关系数据库的 一般规则：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"id":"6f95fdd1-39fc-4592-94e6-ac11557aa3ff","page_size":[595,841],"block_position":"6-19"},{"bbox":[99,518,455,531],"type":"text","angle":0,"index":21,"text":"（1） 将每一个实体类型转换成一个关系模式，实体的属性为关系模式的属性。","id":"ff40a223-7531-42bb-9256-f1345b9447db","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"page_size":[595,841],"block_position":"6-20"},{"bbox":[101,533,340,546],"type":"text","angle":0,"index":22,"text":"（2） 对于二元联系，按各种情况处理，如下面所示。","id":"64542988-bdb7-4984-b39d-2a6d3a9e4595","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":6,"page_size":[595,841],"block_position":"6-21"},{"bbox":[89,548,502,755],"index":24,"angle":0,"type":"table_body","img_path":"/","id":"c836cbbb-4976-42c7-bf30-1abbab8c6af5","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
二元\n关系ER图转换成的关系联系的处理主码外码
1:1A\n1\nA-B\n1\nB(2个关系)\n模式A\n模式B(有两种)\n处理方式(1)\n(1)把模式B的主码,联系的属性加入模式A\n处理方式(2):\n(2)把模式A(略)(依据联系的处理方式)\n方式(1):模式B的主码为模式A\n外码\n方式(2):表A的主码为表B的外
的主码,联系的属性加入模式B码
1:MA\n1\nA-B\nM\nB(2个关系)\n模式A\n模式B把模式B的主码,联系的属性加入模式A(略)模式A对应模式B的主码为模式A的外码
M:NA\nN\nA-B\nM\nB(3个关系)\n模式A\n模式B\n模式A-B联系类型转换成关系模式A-B;模式A-B的属性(a)联系的属性(b)两端实体类型的主码两端实体类型的主码一起构成模式A-B主码两端实体类型的主码分别为模式A-B的外码
","page_idx":6,"page_size":[595,841],"block_position":"6-22"}],[{"bbox":[89,79,505,438],"index":0,"angle":0,"type":"table_body","lines_deleted":true,"text":"","id":"c836cbbb-4976-42c7-bf30-1abbab8c6af5","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"","page_idx":7,"page_size":[595,841],"block_position":"7-0"},{"bbox":[86,458,505,502],"type":"text","angle":0,"index":1,"text":"SQL数据库的体系结构也是三级结构，但术语与传统关系模型术语不同，在SQL中，关系模式称为\"基本表\"，存储模式称为\"存储文件\"，子模式称为\"视图\"，元组称\"行\"，属性称\"列\"。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"id":"ac4fbfe2-a0cb-412b-a12b-3ec3e5b54339","page_size":[595,841],"block_position":"7-1"},{"bbox":[86,520,240,533],"type":"text","angle":0,"index":2,"text":"SQL数据库体系的结构要点如下：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"id":"94ec58c5-1980-4785-8a8f-a05907d94842","page_size":[595,841],"block_position":"7-2"},{"bbox":[92,536,237,549],"type":"text","angle":0,"index":3,"text":"(1)一个SQL数据库是表的汇集。","id":"51c857a6-7f68-462c-8fcd-8bb6ffe01d9d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-3"},{"bbox":[91,551,394,565],"type":"text","angle":0,"index":4,"text":"(2)一个 SQL 表由行集构成，行是列的序列，每列对应一个数据项。","id":"1cf71d6f-eb65-4d86-846c-86889175075b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-4"},{"bbox":[88,567,504,596],"type":"text","angle":0,"index":5,"text":"(3)表或者是基本表，或者是视图。基本表是实际存储在数据库中的表，视图由是由若干基本表或其他视图构成的表的定义。","id":"dac5a4de-0e51-4b2f-82dc-4447eb8975bd","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-5"},{"bbox":[87,598,499,627],"type":"text","angle":0,"index":6,"text":"(4)一个基本表可以跨一个或多个存储文件，一个存储文件也可存放一个或多个基本表。存储文件与物理文件对应。","id":"417598d5-ef3b-4c84-902e-bbcfa7e18447","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-6"},{"bbox":[91,629,362,643],"type":"text","angle":0,"index":7,"text":"(5)用户可以用 SQL 语句对表进行操作，包括视图和基本表。","id":"0ad6925a-836a-4355-8bd9-cf3c0f4e8104","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-7"},{"bbox":[92,645,329,659],"type":"text","angle":0,"index":8,"text":"(6)SQL 的用户可以是应用程序，也可以是终端用户。","id":"609e09e0-8ffb-4b46-8a87-e202116aad5e","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-8"},{"bbox":[87,676,199,689],"type":"text","angle":0,"index":10,"text":"常用SQL语句分为三类：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"id":"bcaadf09-faa3-4970-b918-321574111c2e","page_size":[595,841],"block_position":"7-9"},{"bbox":[90,692,503,705],"type":"text","angle":0,"index":11,"text":"(1)数据定义：DDL：CREATE、ALTER、DROP，定义 SQL 模式，可以是基本表、视图和索引。","id":"b60b3bb4-dde5-4b74-82d8-f3604a90b2d7","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-10"},{"bbox":[88,707,499,735],"type":"text","angle":0,"index":12,"text":"(2)数据操纵：DML：SELECT、INSERT、UPDATE、DELETE，包括数据查询和数据更新(增、删、改)。","id":"0e76a75c-5f10-4ec6-bdea-d60b97c49e92","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-11"},{"bbox":[91,738,499,752],"type":"text","angle":0,"index":13,"text":"(3)数据控制：DCL：GRANT、REVOKE，包括对基本表和视图的授权、完整性规则的描述，","id":"87c91b65-d427-4468-bc24-8b371a8894ad","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":7,"page_size":[595,841],"block_position":"7-12"}],[{"bbox":[86,79,241,91],"type":"text","angle":0,"index":0,"text":"事务控制等。（第四章安全性讲）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"bde795ac-a465-408b-9939-9c80ae5fb5bb","page_size":[595,841],"block_position":"8-0"},{"bbox":[86,95,219,107],"type":"title","angle":0,"index":1,"text":"# 2.1 SQL提供的基本数据类型","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"d1295888-08b1-4c94-9f97-7e41619eac08","page_size":[595,841],"block_position":"8-1"},{"bbox":[86,111,356,122],"type":"text","angle":0,"index":2,"text":"数值型：包括 int、smallint、decimal(p，d)、numeric(p，d)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"54c521bc-0765-4343-bd36-06f01c73c70e","page_size":[595,841],"block_position":"8-2"},{"bbox":[86,125,480,138],"type":"text","angle":0,"index":3,"text":"字符串型：char(n) 、nchar(n)、varchar(n)、nvarchar(n)前 2 者是定长，后 2 者为变长串","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"4ed4c743-f291-4d6d-836c-3e0b92e4f866","page_size":[595,841],"block_position":"8-3"},{"bbox":[86,142,188,153],"type":"text","angle":0,"index":4,"text":"时间型：datetime。 。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"fdd20b05-f21f-427e-a079-22ef3ae74a7d","page_size":[595,841],"block_position":"8-4"},{"bbox":[86,173,232,185],"type":"title","angle":0,"index":5,"text":"# 2.2 基本表的创建、修改和撤消","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"91794eef-a0d5-4c71-afde-f776b4050ea4","page_size":[595,841],"block_position":"8-5"},{"bbox":[87,188,234,200],"type":"title","angle":0,"index":6,"text":"# (1)基本表的创建：(建立表结构)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"02ccc94d-c9ca-4a49-bf51-bfc90970a1ee","page_size":[595,841],"block_position":"8-6"},{"bbox":[92,204,198,216],"type":"text","angle":0,"index":7,"text":"CREATE TABLE 基本表名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"59f7c72b-6a36-4b47-a052-3d4ed881eb83","page_size":[595,841],"block_position":"8-7"},{"bbox":[87,219,149,232],"type":"text","angle":0,"index":8,"text":"(列名，类型，","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"a05adb28-7b1e-4a36-8ddc-93ad37ceaa72","page_size":[595,841],"block_position":"8-8"},{"bbox":[87,250,153,263],"type":"text","angle":0,"index":10,"text":"完整性约束...)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"1bfa7070-a786-4db0-9be5-d04b562cd772","page_size":[595,841],"block_position":"8-9"},{"bbox":[86,265,467,279],"type":"text","angle":0,"index":11,"text":"完整性约束包括主键子句(PRIMARY KEY)、检查子句(CHECK)和外键子句(Foreign KEY).","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"52531cff-120f-4ab6-a3b5-7d2573aa3a7c","page_size":[595,841],"block_position":"8-10"},{"bbox":[87,281,186,294],"type":"title","angle":0,"index":12,"text":"# (2)基本表结构的修改","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"4dd253de-18bc-47d9-9956-32cd42ae8379","page_size":[595,841],"block_position":"8-11"},{"bbox":[87,297,136,309],"type":"text","angle":0,"index":13,"text":"增加新列：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"be788062-a6a0-4b1f-a137-adf59cbb15a6","page_size":[595,841],"block_position":"8-12"},{"bbox":[86,312,256,325],"type":"text","angle":0,"index":14,"text":"ALTER TABLE 基本表名 ADD 列名 类型","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"48169af5-b83e-4237-b487-13ef21e4e588","page_size":[595,841],"block_position":"8-13"},{"bbox":[87,327,158,340],"type":"text","angle":0,"index":15,"text":"删除原有的列：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"e7165e6f-2871-4241-86e2-58ab82630f85","page_size":[595,841],"block_position":"8-14"},{"bbox":[86,344,279,356],"type":"text","angle":0,"index":16,"text":"ALTER TABLE 基本表名 DROP COLUMN 列名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"4cc75d2b-9014-4748-8187-3f4436af7a5b","page_size":[595,841],"block_position":"8-15"},{"bbox":[86,359,367,372],"type":"text","angle":0,"index":17,"text":"修改数据列，只能修改数据列的数据类型，注意其中的限制：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"14548c94-6355-44d3-841e-b2c298acfda2","page_size":[595,841],"block_position":"8-16"},{"bbox":[96,375,356,387],"type":"text","angle":0,"index":18,"text":"ALTER TABLE 基本表名 ALTER COLUMN 列名 新的数据类型","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"411eb938-60df-4be5-97f7-6531655f910a","page_size":[595,841],"block_position":"8-17"},{"bbox":[87,391,164,402],"type":"title","angle":0,"index":19,"text":"# (3)基本表的撤消","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"e1b14ce7-ccd1-43b7-9e83-c9a6d560cc3f","page_size":[595,841],"block_position":"8-18"},{"bbox":[87,407,186,418],"type":"text","angle":0,"index":20,"text":"DROP TABLE 基本表名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"bc90459c-538c-4120-a5aa-e4d3e2c0cf53","page_size":[595,841],"block_position":"8-19"},{"bbox":[86,437,190,449],"type":"title","angle":0,"index":21,"text":"# 2.3 索引的创建和撤消","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"42903dd6-352e-4b55-8c63-6575ff9f187e","page_size":[595,841],"block_position":"8-20"},{"bbox":[87,453,158,465],"type":"title","angle":0,"index":22,"text":"# (1)索引的创建：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"43b530de-8308-4ef5-a09f-a4edc297da77","page_size":[595,841],"block_position":"8-21"},{"bbox":[86,469,399,481],"type":"text","angle":0,"index":23,"text":"CREATE [CLUSTERED][UNIQUE] INDEX 索引名 ON 表名(列名[ASC|DESC])","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"3ad32138-396e-469d-a683-d91231de93ae","page_size":[595,841],"block_position":"8-22"},{"bbox":[87,484,158,497],"type":"title","angle":0,"index":24,"text":"# (2)索引的撤消：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"ff014dd2-71a3-45fb-9c92-367494ef8c38","page_size":[595,841],"block_position":"8-23"},{"bbox":[87,500,200,512],"type":"text","angle":0,"index":25,"text":"DROP INDEX 表名.索引名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"ab1ea9d1-6388-45a1-82e6-756a1b3a1335","page_size":[595,841],"block_position":"8-24"},{"bbox":[86,515,324,528],"type":"text","angle":0,"index":26,"text":"索引的作用，索引的分类（聚餐索引和非聚餐索引）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"affb415b-d641-4021-bc67-62e77d6f30bb","page_size":[595,841],"block_position":"8-25"},{"bbox":[87,531,211,543],"type":"title","angle":0,"index":27,"text":"# 3.1 SELECT 语句的基本句法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"453b82ff-70e0-43bd-87b4-2c36c49ee406","page_size":[595,841],"block_position":"8-26"},{"bbox":[87,546,247,559],"type":"text","angle":0,"index":28,"text":"考核要求：达到“综合应用”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"7603ca6e-3b95-44fc-97d1-5e8f6b49279b","page_size":[595,841],"block_position":"8-27"},{"bbox":[86,562,280,575],"type":"text","angle":0,"index":29,"text":"知识点：SELECT-FROM-WHERE 句型的应用","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"ff77c044-ca2e-41b0-b17a-8cec59c4f35e","page_size":[595,841],"block_position":"8-28"},{"bbox":[95,593,235,606],"type":"title","angle":0,"index":30,"text":"# (1) SELECT-FROM-WHERE 句型","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"e45f2778-7deb-48c6-b813-31f6976fa30c","page_size":[595,841],"block_position":"8-29"},{"bbox":[115,609,230,621],"type":"text","angle":0,"index":31,"text":"SELECT 列名表(逗号隔开)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"d977a6b5-c21d-493f-b0ee-1083f14c7b50","page_size":[595,841],"block_position":"8-30"},{"bbox":[86,624,202,637],"type":"title","angle":0,"index":32,"text":"# FROM 基本表或视图序列","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":8,"id":"a766891f-49da-40b5-b141-cba44a283f0b","page_size":[595,841],"block_position":"8-31"},{"bbox":[87,640,177,652],"type":"text","angle":0,"index":33,"text":"WHERE 条件表达式","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"ce70ca32-d4e9-46b4-93eb-cbc837658d3d","page_size":[595,841],"block_position":"8-32"},{"bbox":[86,655,290,668],"type":"text","angle":0,"index":34,"text":"Notice:掌握条件表达式中各种运算符的应用.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"ab0dfa7f-eb78-45f7-9def-1ecf15d3c848","page_size":[595,841],"block_position":"8-33"},{"bbox":[99,678,268,692],"type":"text","angle":0,"index":35,"text":"算术比较运算符 $\\dot { } = \\mathbf { \\nabla }$ ， $> , < , < >$ 或! $! = , < = , > =$ ；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"1b29fd9f-e8ae-4361-a839-e8a0b2fa5fd9","page_size":[595,841],"block_position":"8-34"},{"bbox":[100,694,233,707],"type":"text","angle":0,"index":36,"text":"逻辑运算符AND、OR、NOT；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"89f72f0f-ea87-4a08-b355-2b702a650145","page_size":[595,841],"block_position":"8-35"},{"bbox":[99,710,405,723],"type":"text","angle":0,"index":37,"text":"集合成员资格运算符：IN，NOT IN；like， not like；between and ；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"cc8519a8-ee7e-40c7-b930-8de41de57744","page_size":[595,841],"block_position":"8-36"},{"bbox":[100,725,267,738],"type":"text","angle":0,"index":38,"text":"谓词:EXISTS(存在量词)，NOT EXISTS；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"e977ba87-3e2c-47c5-a158-6a67785c6909","page_size":[595,841],"block_position":"8-37"},{"bbox":[100,740,222,754],"type":"text","angle":0,"index":39,"text":"聚合函数：（在下面介绍）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":8,"id":"044e580e-d37b-4ece-b59a-8898e3d9e259","page_size":[595,841],"block_position":"8-38"}],[{"bbox":[87,79,199,91],"type":"title","angle":0,"index":0,"text":"# (2) SELECT 句型使用实例","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"ff1ec8ff-8400-4212-8b98-119418a75a5c","page_size":[595,841],"block_position":"9-0"},{"bbox":[86,95,294,107],"type":"text","angle":0,"index":1,"text":"本节内容需要多看例题，多作习题进行掌握。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"00cec9f3-7d51-4d6f-9a40-dfd900668955","page_size":[595,841],"block_position":"9-1"},{"bbox":[86,110,339,122],"type":"text","angle":0,"index":2,"text":"Notice:嵌套的 SELECT 语句的用法 ，体会结构化的含义。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"3f710949-6ad3-44a5-a1d6-28be903feab7","page_size":[595,841],"block_position":"9-2"},{"bbox":[87,126,144,137],"type":"title","angle":0,"index":3,"text":"# (3)聚合函数","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"6adecc45-aaa7-486a-8a90-c85b9198c44e","page_size":[595,841],"block_position":"9-3"},{"bbox":[87,141,189,153],"type":"text","angle":0,"index":4,"text":"注意各个函数的含义：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"f9475d67-f377-4f62-974f-b530553f51be","page_size":[595,841],"block_position":"9-4"},{"bbox":[86,154,334,380],"index":5,"angle":0,"type":"table_body","img_path":"/","id":"68b97bbb-61a7-4d4d-9908-7fb6f90ad097","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
COUNT (*)计算元组的个数
COUNT (列名)求一列中值的计算个数
COUNT(DISTINCT 列名)求一列中值的种类数
SUM (列名)求一列中值的总和
AVG (列名)求一列中值的平均值
MAX (列名)求一列中值的最大值
MIN (列名)求一列中值的最小值
","page_idx":9,"page_size":[595,841],"block_position":"9-5"},{"bbox":[86,383,474,396],"type":"text","angle":0,"index":6,"text":"如果语句没有 Group By 则返回单个值；如果语句带 Group By 则每个小组返回一个值。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"32021a76-2261-4819-9ee2-785f638c37f4","page_size":[595,841],"block_position":"9-6"},{"bbox":[87,398,202,412],"type":"text","angle":0,"index":7,"text":"SELECT 列名表(逗号隔开)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"5f4d1711-534c-4f1f-9da5-c82737e9d29e","page_size":[595,841],"block_position":"9-7"},{"bbox":[87,414,202,427],"type":"text","angle":0,"index":8,"text":"FROM 基本表或视图序列","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"94c82e4a-63f2-49da-bc6f-12feab756b54","page_size":[595,841],"block_position":"9-8"},{"bbox":[87,430,244,443],"type":"text","angle":0,"index":9,"text":"[WHERE 条件表达式] (行条件子句)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"14866bf2-c9c6-44ee-a553-ccef57bc257a","page_size":[595,841],"block_position":"9-9"},{"bbox":[87,445,236,459],"type":"text","angle":0,"index":10,"text":"[GROUP BY 列名序列] (分组子句)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"2c1f4ab6-c4e4-4a9a-a63e-182616b09e21","page_size":[595,841],"block_position":"9-10"},{"bbox":[96,461,266,474],"type":"text","angle":0,"index":11,"text":"[HAVING 组条件表达式] (组条件子句)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"025324fd-316e-4ddf-aa5f-1cf088e0ba37","page_size":[595,841],"block_position":"9-11"},{"bbox":[87,476,268,490],"type":"text","angle":0,"index":12,"text":"[ORDER BY 列名[ASC|DESC]..] (排序子句)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"7660681c-9df5-41a2-a03e-3e5022f2962b","page_size":[595,841],"block_position":"9-12"},{"bbox":[88,492,198,505],"type":"title","angle":0,"index":13,"text":"# (1)SELECT 子句中的规定","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"9b3eabcb-2102-4b91-b647-bcc80fff4464","page_size":[595,841],"block_position":"9-13"},{"bbox":[104,507,453,520],"type":"text","angle":0,"index":14,"text":" 如果要求输出表格中不允许出现重复元组，则在 SELECT 后加一 DISTINCT","id":"138b9eb9-f0b0-4496-9393-b2f4cee3ca0e","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"page_size":[595,841],"block_position":"9-14"},{"bbox":[104,523,431,536],"type":"text","angle":0,"index":15,"text":" SELECT 子句中允许出现 ${ + , ^ { - } , ^ { * } , / } ,$ ,以及列名、常数、函数的算术表达式","id":"1f066251-1e7e-4bce-844b-b1d57d2bdb3b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"page_size":[595,841],"block_position":"9-15"},{"bbox":[87,539,230,552],"type":"title","angle":0,"index":17,"text":"# (2) 条件表达式的算术比较操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"dcd73099-5114-40e6-aca8-13c003187f1f","page_size":[595,841],"block_position":"9-16"},{"bbox":[104,555,397,567],"type":"text","angle":0,"index":18,"text":" WHERE 子句中可以用 BETWEEN...AND...来限定一个值的范围","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"fbc87fc8-db4a-4ad1-9c55-209a10eddbc6","page_size":[595,841],"block_position":"9-17"},{"bbox":[88,570,207,582],"type":"title","angle":0,"index":19,"text":"# (3)列和基本表的改名操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"265a5356-5a49-4365-a2e7-9e2889adb8af","page_size":[595,841],"block_position":"9-18"},{"bbox":[104,586,406,598],"type":"text","angle":0,"index":20,"text":" 同一个基本表在 SELECT语句中多次引用时可用AS来增加别名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"ed058260-31ac-43d9-9269-c6020aba612f","page_size":[595,841],"block_position":"9-19"},{"bbox":[88,601,186,614],"type":"title","angle":0,"index":21,"text":"# (4)字符串的匹配操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"56284db2-2c52-4e8b-b28c-530a8d494e74","page_size":[595,841],"block_position":"9-20"},{"bbox":[104,617,406,630],"type":"text","angle":0,"index":22,"text":" WHERE 子句中字符串匹配用 LIKE 和两个通配符，%和下划线_.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"3fea9baf-2570-4353-bb48-982f23d02f76","page_size":[595,841],"block_position":"9-21"},{"bbox":[87,648,207,661],"type":"title","angle":0,"index":23,"text":"# (5)集合的并、交、差操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"a0b51993-278a-4f9b-91fa-07ce97ed095e","page_size":[595,841],"block_position":"9-22"},{"bbox":[104,664,504,692],"type":"text","angle":0,"index":24,"text":" 查询结果的结构完全一致时，可将两个查询进行并(UNION)、交（InterSect）、差（Except）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"3eb34f96-011c-4ac7-b017-e4a1d5acd091","page_size":[595,841],"block_position":"9-23"},{"bbox":[88,695,175,708],"type":"title","angle":0,"index":25,"text":"# (6)空值的比较操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"dad97694-e38f-4886-8b74-a70644b71d97","page_size":[595,841],"block_position":"9-24"},{"bbox":[104,710,352,724],"type":"text","angle":0,"index":26,"text":"查询空值操作不是用 $= \"$ null',而是用 IS NULL 来测试。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"13d5da57-9677-4007-82d6-96bfcb283f09","page_size":[595,841],"block_position":"9-25"},{"bbox":[88,726,175,739],"type":"title","angle":0,"index":27,"text":"# (7)集合的比较操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":9,"id":"2f7bf026-a24c-4f84-96af-e9534b482fd3","page_size":[595,841],"block_position":"9-26"},{"bbox":[105,742,267,755],"type":"text","angle":0,"index":28,"text":" 集合成员资格比较用 IN/NOT IN","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":9,"id":"15639f68-e7a2-4949-8d84-9a3620987dd0","page_size":[595,841],"block_position":"9-27"}],[{"bbox":[104,79,431,91],"type":"text","angle":0,"index":0,"text":" 集合成员算术比较用元组 θ ANY/ALL (θ 是算术比较运算符）（少用）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"3fe25b9f-187c-4551-a724-0a87f97cdd7e","page_size":[595,841],"block_position":"10-0"},{"bbox":[88,95,167,107],"type":"title","angle":0,"index":1,"text":"# (8) 导出表的使用","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"bc29f10d-7dd8-4ba4-bd79-23318cb644da","page_size":[595,841],"block_position":"10-1"},{"bbox":[104,110,438,122],"type":"text","angle":0,"index":2,"text":" 使用 INTO 关键字，可以给子查询结果起个表名，保存相关查询数据。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"c1bef2f2-311f-405c-a8ed-3b4b0fbc254b","page_size":[595,841],"block_position":"10-2"},{"bbox":[88,126,189,138],"type":"title","angle":0,"index":3,"text":"# (9) 基本表的连接操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"51cd3ccf-b53e-466b-8144-4732095afe17","page_size":[595,841],"block_position":"10-3"},{"bbox":[104,141,317,154],"type":"text","angle":0,"index":4,"text":"等值连接操作是用 [INNER] JOIN 来实现的。","id":"66a9ef1b-4fe6-410e-a36c-0b5ca4ab9946","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"page_size":[595,841],"block_position":"10-4"},{"bbox":[88,157,504,200],"type":"text","angle":0,"index":5,"text":"外连接：左外连接 LEFT [OUTER] JOIN 、RIGHT [OUTER] JOIN、FULL [OUTER] JOIN自身连接：通过设置别名的方法，一个 SELECT语句中可以对一个表进行多次扫描，实现连接。","id":"c5330a37-553b-46ac-9464-b5dd995616c3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"page_size":[595,841],"block_position":"10-5"},{"bbox":[88,203,189,216],"type":"title","angle":0,"index":7,"text":"# 数据插入方式有两种：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"61995cbe-4eee-4e16-8ec4-23b0109742bd","page_size":[595,841],"block_position":"10-6"},{"bbox":[88,219,167,232],"type":"title","angle":0,"index":8,"text":"# (1) 元组值的插入","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"38a5ab5a-1054-428a-9e20-98b977d3439b","page_size":[595,841],"block_position":"10-7"},{"bbox":[88,235,226,248],"type":"text","angle":0,"index":9,"text":"INSERT INTO 基本表名(列名表)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"bdb8b3e1-d71e-4a07-b654-ead757a3a52f","page_size":[595,841],"block_position":"10-8"},{"bbox":[88,251,155,263],"type":"text","angle":0,"index":10,"text":"values(元组值)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"bb4e759d-1e13-47d8-9ebb-b0d94a2cf6e8","page_size":[595,841],"block_position":"10-9"},{"bbox":[88,266,177,279],"type":"title","angle":0,"index":11,"text":"# (2) 查询结果的插入","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"c6794a73-9fe0-4474-95e8-512c4d799200","page_size":[595,841],"block_position":"10-10"},{"bbox":[88,281,226,294],"type":"text","angle":0,"index":12,"text":"INSERT INTO 基本表名(列名表)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"553650e7-3ae3-4b1f-9a99-7c426d98014e","page_size":[595,841],"block_position":"10-11"},{"bbox":[88,297,164,309],"type":"text","angle":0,"index":13,"text":"SELECT 查询语句","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"764228c2-bd51-461a-a84f-e2473e65b2d3","page_size":[595,841],"block_position":"10-12"},{"bbox":[88,312,229,325],"type":"text","angle":0,"index":14,"text":"WHERE子句中使用下列关键字","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"ec0831a3-0fd2-472f-820a-64b86c1bc343","page_size":[595,841],"block_position":"10-13"},{"bbox":[88,328,294,341],"type":"text","angle":0,"index":15,"text":"除了比较符，可以在 WHERE 子句中使用下列","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"30c6ad25-64a1-41d8-8e36-6ef51af4583b","page_size":[595,841],"block_position":"10-14"},{"bbox":[88,343,121,356],"type":"text","angle":0,"index":16,"text":"关键字","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"7de902da-1c8e-4650-b1ce-e508799228d8","page_size":[595,841],"block_position":"10-15"},{"bbox":[88,359,121,372],"type":"title","angle":0,"index":17,"text":"# 关键字","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"47b15a44-31bb-450f-812a-5b748ea16b0e","page_size":[595,841],"block_position":"10-16"},{"bbox":[88,375,111,387],"type":"title","angle":0,"index":18,"text":"# 含义","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":10,"id":"bde0d769-4a87-4a13-bd78-bb8635096de9","page_size":[595,841],"block_position":"10-17"},{"bbox":[88,391,99,401],"type":"text","angle":0,"index":19,"text":"IN","color":{"line":"rgba(13, 83, 222, 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1)"},"page_idx":10,"id":"c786dee9-913a-44c0-a9c0-c373502eb782","page_size":[595,841],"block_position":"10-21"},{"bbox":[88,454,108,464],"type":"text","angle":0,"index":23,"text":"LIKE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"39af3415-7782-433e-b9a1-4cd53bdf2509","page_size":[595,841],"block_position":"10-22"},{"bbox":[88,468,237,481],"type":"text","angle":0,"index":24,"text":"判断值是否与一个给定的值相似","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"0e202ddf-7e4a-4718-9b8f-a8bfd442a482","page_size":[595,841],"block_position":"10-23"},{"bbox":[88,485,129,495],"type":"text","angle":0,"index":25,"text":"NOT LIKE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"6231fcb0-56c2-4ae5-abcb-6da6fc72b677","page_size":[595,841],"block_position":"10-24"},{"bbox":[88,500,247,513],"type":"text","angle":0,"index":26,"text":"判断值是否与一个给定的值不相似","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"befa17e5-0d39-48a9-9157-3105105a1310","page_size":[595,841],"block_position":"10-25"},{"bbox":[88,516,122,526],"type":"text","angle":0,"index":27,"text":"IS NULL","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"91413aa9-b33b-4a9c-9fa1-cc4a24e9230f","page_size":[595,841],"block_position":"10-26"},{"bbox":[88,531,163,543],"type":"text","angle":0,"index":28,"text":"判断值是否为空","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"be4d4ef7-5f0c-4196-ad1d-6d3525267cc0","page_size":[595,841],"block_position":"10-27"},{"bbox":[88,547,143,557],"type":"text","angle":0,"index":29,"text":"IS NOT NULL","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"80c68c3f-481f-4469-addf-49a710777e42","page_size":[595,841],"block_position":"10-28"},{"bbox":[88,562,174,574],"type":"text","angle":0,"index":30,"text":"判断值是否不为空","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"37ec10f0-b278-4842-8303-2a008f7743ab","page_size":[595,841],"block_position":"10-29"},{"bbox":[88,578,110,588],"type":"text","angle":0,"index":31,"text":"AND","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"0511633c-2de5-4513-b57d-223474ff3e2f","page_size":[595,841],"block_position":"10-30"},{"bbox":[88,593,249,605],"type":"text","angle":0,"index":32,"text":"判断是否满足AND两边所给的条件","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"1f0cdbc7-d8a5-45e7-a3ca-c70435bc3e2c","page_size":[595,841],"block_position":"10-31"},{"bbox":[88,609,102,619],"type":"text","angle":0,"index":33,"text":"OR","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"46346ab7-16f6-4f5d-82ac-dff6151bf8d1","page_size":[595,841],"block_position":"10-32"},{"bbox":[88,624,285,637],"type":"text","angle":0,"index":34,"text":"判断是否满足OR 两边所给的条件中的一个","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"f01335dd-2f4d-4f6e-b4e5-7f664e5dbded","page_size":[595,841],"block_position":"10-33"},{"bbox":[88,640,158,650],"type":"text","angle":0,"index":35,"text":"BETWEEN…AND","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"77290e83-4353-4a81-a331-c826644bedf0","page_size":[595,841],"block_position":"10-34"},{"bbox":[88,655,215,668],"type":"text","angle":0,"index":36,"text":"判断值是否在所给的值之间","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"f48e2184-ae2a-4ba7-89d1-c326feae0010","page_size":[595,841],"block_position":"10-35"},{"bbox":[88,671,180,682],"type":"text","angle":0,"index":37,"text":"NOT BETWEEN…AND","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"db419bb3-f904-4ace-a1cc-cabd04e95b62","page_size":[595,841],"block_position":"10-36"},{"bbox":[88,687,226,699],"type":"text","angle":0,"index":38,"text":"判断值是否不在所给的值之间","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"4a5b9219-04ad-4b3b-9acb-4a62b3b913f2","page_size":[595,841],"block_position":"10-37"},{"bbox":[88,703,305,714],"type":"text","angle":0,"index":39,"text":"使用 LIKE 运算符可以完成对字符串的模糊匹配。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"c4e546b2-6c75-42df-ae00-4e708f82281f","page_size":[595,841],"block_position":"10-38"},{"bbox":[88,719,96,729],"type":"text","angle":0,"index":40,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"72c9e7de-cec1-4f46-8971-c850b338c4d7","page_size":[595,841],"block_position":"10-39"},{"bbox":[88,734,136,745],"type":"text","angle":0,"index":41,"text":"基本语法：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"f6bc5da7-355c-4778-adf8-278eebceb964","page_size":[595,841],"block_position":"10-40"},{"bbox":[88,749,165,761],"type":"text","angle":0,"index":42,"text":"SELECT select_list","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":10,"id":"ffbe0105-7687-4d63-a480-cfbde3e12a2e","page_size":[595,841],"block_position":"10-41"}],[{"bbox":[86,79,174,91],"type":"text","angle":0,"index":0,"text":"FROM table_sourse","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"a75ad920-878b-4180-9507-7cc4b6c42875","page_size":[595,841],"block_position":"11-0"},{"bbox":[87,95,236,106],"type":"text","angle":0,"index":1,"text":"WHERE EXPRESSION LIKE ‘STRING’","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"7efe8411-53d3-4f06-9ecb-1c9b215c4353","page_size":[595,841],"block_position":"11-1"},{"bbox":[88,111,96,121],"type":"text","angle":0,"index":2,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"bc87797b-2000-4e5c-afe8-147f098f5b00","page_size":[595,841],"block_position":"11-2"},{"bbox":[87,125,313,138],"type":"text","angle":0,"index":3,"text":"其中，EXPRESSION 为用作选择条件的列或表达式","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"11cd8372-8d9f-4ede-ae69-87349c0bc6cc","page_size":[595,841],"block_position":"11-3"},{"bbox":[88,143,96,153],"type":"text","angle":0,"index":4,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"be59faa4-ec41-43b8-91f8-aa89ceaa1899","page_size":[595,841],"block_position":"11-4"},{"bbox":[87,157,273,169],"type":"text","angle":0,"index":5,"text":"指定的字符串中可以包含通配符，包括：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"9a93d369-56c5-44cb-8458-973eeba5a928","page_size":[595,841],"block_position":"11-5"},{"bbox":[89,173,249,186],"type":"text","angle":0,"index":6,"text":"%：代表任意多个字符。例：%jing","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"481a2c12-64cb-4f5d-a948-4c9e8fd6b04b","page_size":[595,841],"block_position":"11-6"},{"bbox":[89,188,282,201],"type":"text","angle":0,"index":7,"text":"_（下划线）：代表单个字符。例：_ouse","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"13e2be35-ec8f-4bea-a7c4-9c8641a79ae1","page_size":[595,841],"block_position":"11-7"},{"bbox":[89,203,309,217],"type":"text","angle":0,"index":8,"text":"[ ]：代表指定范围内的单个字符。例：[mh]ouse","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"9fa88ccf-0cad-482b-9079-dff93e48ffb9","page_size":[595,841],"block_position":"11-8"},{"bbox":[89,219,342,232],"type":"text","angle":0,"index":9,"text":"[^ ]：代表不再指定范围内的单个字符。例：[^mh]ouse","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"84b3eda2-82db-4520-811c-2c93a2a92dca","page_size":[595,841],"block_position":"11-9"},{"bbox":[86,250,282,263],"type":"text","angle":0,"index":10,"text":"WHERE子句中，也可以使用逻辑运算符来","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"aeafafda-b5cb-40dd-90a1-ce1d3ecbd632","page_size":[595,841],"block_position":"11-10"},{"bbox":[87,266,157,279],"type":"text","angle":0,"index":11,"text":"连接多个条件。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"34c03056-f0c5-4774-9201-1bc8bf3b1247","page_size":[595,841],"block_position":"11-11"},{"bbox":[88,284,96,292],"type":"text","angle":0,"index":12,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"27b9bafe-c92a-4ddb-87c3-27a4e86c7d60","page_size":[595,841],"block_position":"11-12"},{"bbox":[88,296,178,310],"type":"text","angle":0,"index":13,"text":"主要有逻辑运算符：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"e6c471d1-538d-472c-ac91-586ac9d2cf28","page_size":[595,841],"block_position":"11-13"},{"bbox":[88,313,110,323],"type":"text","angle":0,"index":14,"text":"AND","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"a831fb54-5254-4564-9656-bd9c3c43d494","page_size":[595,841],"block_position":"11-14"},{"bbox":[88,328,104,338],"type":"text","angle":0,"index":15,"text":"OR","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"6aafc460-ae2c-4b58-831a-83b167f58c6d","page_size":[595,841],"block_position":"11-15"},{"bbox":[88,343,109,354],"type":"text","angle":0,"index":16,"text":"NOT","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"c9668e4a-94d9-4c45-9e8f-7e3079ee2f02","page_size":[595,841],"block_position":"11-16"},{"bbox":[87,359,166,372],"type":"title","angle":0,"index":17,"text":"# 4.2 SQL 数据删除","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":11,"id":"f378989c-cb61-45ca-84e2-aab91d083a16","page_size":[595,841],"block_position":"11-17"},{"bbox":[87,375,248,388],"type":"text","angle":0,"index":18,"text":"考核要求：达到“综合应用”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"5e6360af-d99b-44fb-8744-6d48a2b749e4","page_size":[595,841],"block_position":"11-18"},{"bbox":[88,407,290,419],"type":"text","angle":0,"index":19,"text":"DELETE FROM 基本表名 [WHERE 条件表达式]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"6a531bde-afc6-47d4-b19f-74e57c0bd0ee","page_size":[595,841],"block_position":"11-19"},{"bbox":[94,421,314,434],"type":"text","angle":0,"index":20,"text":"（语义：从基本表中删除满足条件表达式的元组）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"1eaccf07-c7c0-453a-ac0b-3171f2a46f08","page_size":[595,841],"block_position":"11-20"},{"bbox":[88,437,207,449],"type":"text","angle":0,"index":21,"text":"注意带子查询的数据删除","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"978a74b3-b4c9-4bb2-8499-07adc8940b5c","page_size":[595,841],"block_position":"11-21"},{"bbox":[87,453,352,465],"type":"text","angle":0,"index":22,"text":"示例：求有两门以上不及格课程同学的学号及其平均成绩","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"e2407139-4175-4235-a2dd-0e4e1bd5da40","page_size":[595,841],"block_position":"11-22"},{"bbox":[88,469,216,481],"type":"text","angle":0,"index":23,"text":"Select S#, Avg(Score) From SC","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"20b6b358-47db-4fbc-82f3-7e8519bfafbe","page_size":[595,841],"block_position":"11-23"},{"bbox":[88,485,166,495],"type":"text","angle":0,"index":24,"text":"Where Score $< 6 0$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"47e4ea30-c30b-49f0-89d8-876f8a7780e5","page_size":[595,841],"block_position":"11-24"},{"bbox":[88,500,226,512],"type":"text","angle":0,"index":25,"text":"Group by S# Having Count $^ { ( * ) } ) { > } 2$ ;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"026408e0-24ab-4ab7-b293-44460c5900d9","page_size":[595,841],"block_position":"11-25"},{"bbox":[87,514,458,544],"type":"text","angle":0,"index":26,"text":"Ø该SQL语句求出的是“该同学那几门不及格课程的平均成绩”，而不是 “该同学所有课程的平均成绩” 。因此正确写法为：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"3ef404b8-ec25-439e-8cad-c0967fb89815","page_size":[595,841],"block_position":"11-26"},{"bbox":[88,546,216,559],"type":"text","angle":0,"index":27,"text":"Select S#, Avg(Score) From SC","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"721672c5-c912-49be-9be6-4bbca24a3722","page_size":[595,841],"block_position":"11-27"},{"bbox":[88,562,142,573],"type":"text","angle":0,"index":28,"text":"Where S# in","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"dda947bd-35e5-4ef8-ac75-b4f6d55739e9","page_size":[595,841],"block_position":"11-28"},{"bbox":[88,577,171,589],"type":"text","angle":0,"index":29,"text":"( Select S# From SC","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"d7971607-59e0-4b23-9eb0-84d1cbbebc5b","page_size":[595,841],"block_position":"11-29"},{"bbox":[88,593,166,604],"type":"text","angle":0,"index":30,"text":"Where Score < 60","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"721a67ce-1718-4c9a-9219-8baa5ce415e4","page_size":[595,841],"block_position":"11-30"},{"bbox":[88,608,228,621],"type":"text","angle":0,"index":31,"text":"Group by S# Having Count $^ { ( * ) } ) { > } 2$ )","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"04a40742-2644-47ab-82fc-db842b5885a5","page_size":[595,841],"block_position":"11-31"},{"bbox":[88,625,142,636],"type":"text","angle":0,"index":32,"text":"Group by S#","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"f786c22e-17a9-413b-8061-329a27f60acb","page_size":[595,841],"block_position":"11-32"},{"bbox":[88,640,132,652],"type":"text","angle":0,"index":33,"text":"交叉连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"c5a7f3eb-bbf6-440f-805a-d78509a7b391","page_size":[595,841],"block_position":"11-33"},{"bbox":[87,655,336,684],"type":"text","angle":0,"index":34,"text":"也叫非限制连接，将两个表不加任何约束的组合起来，即两个表的广义笛卡尔积。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"4b66d225-7636-403d-84db-4ba6132f5c94","page_size":[595,841],"block_position":"11-34"},{"bbox":[88,689,96,698],"type":"text","angle":0,"index":35,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"f55c751a-8984-4587-8a4b-45432bf7b935","page_size":[595,841],"block_position":"11-35"},{"bbox":[87,702,342,730],"type":"text","angle":0,"index":36,"text":"交叉连接后得到的结果集的行数是两个被连接表的行数的乘积。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"67f18be0-9860-4e9d-8509-e7e5c29bcc56","page_size":[595,841],"block_position":"11-36"},{"bbox":[88,735,96,744],"type":"text","angle":0,"index":37,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"973cef48-308b-4f74-b143-eec9f9feb9d4","page_size":[595,841],"block_position":"11-37"},{"bbox":[88,749,115,761],"type":"text","angle":0,"index":38,"text":"语法：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":11,"id":"93304b6e-5773-4ff4-9d0d-a864f78f370e","page_size":[595,841],"block_position":"11-38"}],[{"bbox":[87,79,229,153],"index":0,"angle":0,"type":"code","text":"```sql\nSELECT select_list \nFROM table1 CROSS JOIN table2 \n或 \nSELECT select_list \nFROM table1, table2\n```","id":"ebcd5777-6fc4-429c-852c-64c71b116997","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":12,"page_size":[595,841],"block_position":"12-0"},{"bbox":[88,157,155,169],"type":"text","angle":0,"index":1,"text":"SQL高级语法：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"9b6d086f-a29e-4ac4-995c-8619f0ceaa35","page_size":[595,841],"block_position":"12-1"},{"bbox":[88,173,117,184],"type":"text","angle":0,"index":2,"text":"Select","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"d06ff610-397d-4e5b-bfa0-c3a7e97e1a24","page_size":[595,841],"block_position":"12-2"},{"bbox":[88,188,110,200],"type":"text","angle":0,"index":3,"text":"列名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"ac873ac3-6883-4088-a5bb-1a537a4c38e4","page_size":[595,841],"block_position":"12-3"},{"bbox":[88,204,145,216],"type":"text","angle":0,"index":4,"text":"[ [, 列名] … ]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"cfc08ddd-1af4-4a31-aff8-422f49a62685","page_size":[595,841],"block_position":"12-4"},{"bbox":[88,220,194,232],"type":"text","angle":0,"index":5,"text":"From 表名 1 [NATURAL]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"520c7130-8a62-411c-be91-f0e2e2769383","page_size":[595,841],"block_position":"12-5"},{"bbox":[88,235,327,263],"index":6,"angle":0,"type":"code","text":"```txt\n[INNER|{LEFT|RIGHT|FULL} [OUTER]] JOIN 表名2 {ON\n```","id":"4bbc480c-863f-410a-a4c7-463eda4b6697","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":12,"page_size":[595,841],"block_position":"12-6"},{"bbox":[88,266,136,280],"type":"text","angle":0,"index":7,"text":"连接条件}","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"e6001eaa-edd7-4c7e-95b4-0fc98290fb5b","page_size":[595,841],"block_position":"12-7"},{"bbox":[88,282,190,295],"type":"text","angle":0,"index":8,"text":"[ Where 检索条件 ] … ;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"c0fd1036-7bbb-41f6-aef2-cc5cecb22d90","page_size":[595,841],"block_position":"12-8"},{"bbox":[88,297,176,310],"type":"text","angle":0,"index":9,"text":"连接中使用 natural","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"d40a4e8f-b73f-413e-8163-16e8c48e5e3c","page_size":[595,841],"block_position":"12-9"},{"bbox":[88,312,426,341],"type":"text","angle":0,"index":10,"text":"q 出现在结果关系中的两个连接关系的元组在公共属性上取值相等，且 公共属性只出现一次","id":"4c10195d-7f26-4c6d-9b1d-e7aa3c0d4a53","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"page_size":[595,841],"block_position":"12-10"},{"bbox":[88,343,220,357],"type":"text","angle":0,"index":11,"text":"$\\varnothing$ 连接中使用 on <连接条件>","id":"d5a1703a-ea5f-45bb-b2a0-5852e9d35bea","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"page_size":[595,841],"block_position":"12-11"},{"bbox":[88,359,423,388],"type":"text","angle":0,"index":12,"text":"q 出现在结果关系中的两个连接关系的元组取值满足连接条件，且公共属性出现两次","id":"f82fe576-5677-48f7-83b7-931607dacfae","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"page_size":[595,841],"block_position":"12-12"},{"bbox":[89,391,171,404],"type":"text","angle":0,"index":14,"text":"内连接(Inner Join)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"a5a4b1a8-93fa-48df-a616-758f7d00a192","page_size":[595,841],"block_position":"12-13"},{"bbox":[88,409,95,416],"type":"text","angle":0,"index":15,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"e1d6cf73-9a39-40af-8726-2759d8e26527","page_size":[595,841],"block_position":"12-14"},{"bbox":[88,422,359,450],"type":"text","angle":0,"index":16,"text":"指定了 INNER 关键字的连接是内连接，内连接按照 ON 所指定的连接条件合并两个表，返回满足条件的行。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"4f1043bc-12ef-4df9-b877-c3ba386e279b","page_size":[595,841],"block_position":"12-15"},{"bbox":[88,455,95,463],"type":"text","angle":0,"index":17,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"64d9e489-b278-43b3-8f51-19c64767aa1a","page_size":[595,841],"block_position":"12-16"},{"bbox":[88,468,362,497],"type":"text","angle":0,"index":18,"text":"内连接是系统默认的，可以省略INNER关键字。使用内连接后仍可使用WHERE子句指定条件。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"a248f778-c712-4afc-b76b-085b2aef5250","page_size":[595,841],"block_position":"12-17"},{"bbox":[88,502,95,510],"type":"text","angle":0,"index":19,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"cbfd8a71-8111-45d9-b064-0716b40de9b1","page_size":[595,841],"block_position":"12-18"},{"bbox":[88,515,330,542],"type":"text","angle":0,"index":20,"text":"如：<表名1>.<列名 $1 > < > <$ 表名 2>.<列名 $_ { 2 > }$ 2024/6/6102","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"30251e52-dbb9-4a23-a75d-045c7d28be7e","page_size":[595,841],"block_position":"12-19"},{"bbox":[88,546,175,560],"type":"text","angle":0,"index":21,"text":"等值连接(EquiJoin)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"1ea33c80-4846-42eb-b39f-2f1e4c96e8bf","page_size":[595,841],"block_position":"12-20"},{"bbox":[88,564,95,571],"type":"text","angle":0,"index":22,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"f9a435a0-7a57-45bc-9f01-2bfe740a7b0f","page_size":[595,841],"block_position":"12-21"},{"bbox":[88,577,314,606],"type":"text","angle":0,"index":23,"text":"使用 $^ { 6 6 } = \\upsilon$ 关系将表连接起来的查询，其查询结果中列出被连接表中的所有列，包括其中的重复列。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"7914bc01-42d6-4b26-972b-1c618914cb57","page_size":[595,841],"block_position":"12-22"},{"bbox":[88,611,95,618],"type":"text","angle":0,"index":24,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"1138dc38-a478-49ed-ad0d-fbdab6f4efc4","page_size":[595,841],"block_position":"12-23"},{"bbox":[88,624,132,637],"type":"text","angle":0,"index":25,"text":"等值连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"2921b0e9-1331-49f9-bd7e-31e270de42b3","page_size":[595,841],"block_position":"12-24"},{"bbox":[88,640,215,652],"type":"text","angle":0,"index":26,"text":"连接运算符为 $=$ 的连接操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"8a00430b-c711-492a-9903-a6eeee13db47","page_size":[595,841],"block_position":"12-25"},{"bbox":[88,655,281,668],"type":"text","angle":0,"index":27,"text":"v [<表名 1>.]<列名 $\\uparrow > =$ [<表名 2>.]<列名 $_ { 2 > }$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"d92d08fe-be67-44e4-bcb0-0af8eebd9c7d","page_size":[595,841],"block_position":"12-26"},{"bbox":[88,671,349,700],"type":"text","angle":0,"index":28,"text":"任何子句中引用表1和表2中同名属性时，都必须加表名前缀。引用唯一属性名时可以加也可以省略表名前缀。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"9ab6b2d8-a03c-4839-993b-533378b88bf4","page_size":[595,841],"block_position":"12-27"},{"bbox":[88,705,95,713],"type":"text","angle":0,"index":29,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"0911a8e5-87d3-4dc1-b44f-7abbc5fad5aa","page_size":[595,841],"block_position":"12-28"},{"bbox":[88,718,356,744],"type":"text","angle":0,"index":30,"text":"表的连接条件经常采用“主码 $\\mathsf { I } \\equiv \\mathsf { I }$ 外部码”的形式。2024/6/6103","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"f032777b-4b74-43f6-9830-7e3b52c2dedc","page_size":[595,841],"block_position":"12-29"},{"bbox":[88,751,95,759],"type":"text","angle":0,"index":31,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":12,"id":"4137060d-d05f-4e22-85bb-56eeada826b5","page_size":[595,841],"block_position":"12-30"}],[{"bbox":[87,79,116,91],"type":"text","angle":0,"index":0,"text":"语法：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"72408ac5-6268-4f6c-91b9-84f3acbf029d","page_size":[595,841],"block_position":"13-0"},{"bbox":[87,95,166,106],"type":"text","angle":0,"index":1,"text":"SELECT select_list","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"5903b5c4-14e5-45ad-8075-a3f4e50568c8","page_size":[595,841],"block_position":"13-1"},{"bbox":[87,109,235,122],"type":"text","angle":0,"index":2,"text":"FROM table1 [INNER] JOIN table2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"e81cb83f-c9e1-45e3-9cd7-7c52ef1dd853","page_size":[595,841],"block_position":"13-2"},{"bbox":[87,126,245,137],"type":"text","angle":0,"index":3,"text":"ON table1.column1=table2.column2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"f47f5bf1-3399-4e5e-b160-465cdfbd1b1d","page_size":[595,841],"block_position":"13-3"},{"bbox":[87,142,101,153],"type":"text","angle":0,"index":4,"text":"和","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"faee5683-b0e3-4822-88e2-19da79ec1b37","page_size":[595,841],"block_position":"13-4"},{"bbox":[87,157,165,169],"type":"text","angle":0,"index":5,"text":"SELECT select_list","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"4e78d512-2d69-47f8-ae66-83557c9be4ae","page_size":[595,841],"block_position":"13-5"},{"bbox":[87,174,185,185],"type":"text","angle":0,"index":6,"text":"FROM table1 ，table2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"2bcebded-5291-4971-851b-3a32da2de448","page_size":[595,841],"block_position":"13-6"},{"bbox":[87,188,262,200],"type":"text","angle":0,"index":7,"text":"WHERE table1.column1=table2.column2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"48989955-857f-4372-b1fa-a3ebf09872dc","page_size":[595,841],"block_position":"13-7"},{"bbox":[86,203,411,217],"type":"text","angle":0,"index":8,"text":"⽰例：按“001”号课成绩由⾼到低顺序显⽰所有学生的姓名(⼆表连接)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"7bd0b3ce-75e6-49ad-a3cc-93b88502b8ed","page_size":[595,841],"block_position":"13-8"},{"bbox":[87,220,117,230],"type":"text","angle":0,"index":9,"text":"Select","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"48c717e7-661b-49ca-bc78-dc0316af2b37","page_size":[595,841],"block_position":"13-9"},{"bbox":[87,235,198,246],"type":"text","angle":0,"index":10,"text":"Sname From Student, SC","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"cab05e8e-e57a-4894-91d6-fe2c0b4af6f2","page_size":[595,841],"block_position":"13-10"},{"bbox":[87,250,279,261],"type":"text","angle":0,"index":11,"text":"Where Student. $\\mathsf { S } \\# = \\mathsf { S C } . \\mathsf { S } \\#$ and SC.C# = ‘001’","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"421f307a-0f66-4055-b5f7-38d198174628","page_size":[595,841],"block_position":"13-11"},{"bbox":[87,266,182,278],"type":"text","angle":0,"index":12,"text":"Order By Score DESC;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"a52e8880-590b-40a2-9833-3488578f9687","page_size":[595,841],"block_position":"13-12"},{"bbox":[86,281,429,294],"type":"text","angle":0,"index":13,"text":"$\\varnothing$ 多表连接时，如两个表的属性名相同，则需采用表名. 属性名方式来限定","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"5230564b-c865-415e-855d-35f78e18aea9","page_size":[595,841],"block_position":"13-13"},{"bbox":[87,297,198,309],"type":"text","angle":0,"index":14,"text":"该 属性是属于哪一个表","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"16cc41cd-7025-4a86-be97-ddac5cdbe7b6","page_size":[595,841],"block_position":"13-14"},{"bbox":[86,312,411,326],"type":"text","angle":0,"index":15,"text":"⽰例：按‘数据库’课成绩由⾼到低顺序显⽰所有同学姓名(三表连接)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"2dbb0077-a327-46a2-9836-c075d20e654f","page_size":[595,841],"block_position":"13-15"},{"bbox":[87,328,117,339],"type":"text","angle":0,"index":16,"text":"Select","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"c8efff7c-96e9-4896-8fac-fcbe834d8e01","page_size":[595,841],"block_position":"13-16"},{"bbox":[87,343,232,355],"type":"text","angle":0,"index":17,"text":"Sname From Student, SC, Course","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"d03edae1-2fba-49fd-9dce-728659ba1365","page_size":[595,841],"block_position":"13-17"},{"bbox":[87,359,120,370],"type":"text","angle":0,"index":18,"text":"Where","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"1df1556f-af0d-436c-9083-c9a4db5b3573","page_size":[595,841],"block_position":"13-18"},{"bbox":[86,375,367,387],"type":"text","angle":0,"index":19,"text":"Student. $S \\# = \\Im \\mathbb { C } . S \\#$ and SC.C# $\\equiv$ Course.C# and Cname $\\equiv$ ‘数据库","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"ebfd97fc-bfef-492c-ad2e-fbdc67537f55","page_size":[595,841],"block_position":"13-19"},{"bbox":[87,391,182,402],"type":"text","angle":0,"index":20,"text":"Order By Score DESC;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"2414c61d-8f6a-4b7a-959b-6aae12c8cdb2","page_size":[595,841],"block_position":"13-20"},{"bbox":[88,406,132,418],"type":"title","angle":0,"index":21,"text":"# 自然连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":13,"id":"db502a21-0334-4164-b44b-f2a5a27ad8a2","page_size":[595,841],"block_position":"13-21"},{"bbox":[87,422,324,434],"type":"text","angle":0,"index":22,"text":"等值连接的一种特殊情况，自动判断相同名称的列，","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"04356c81-53a8-4f9d-a83d-e8f765d19d2f","page_size":[595,841],"block_position":"13-22"},{"bbox":[87,437,304,449],"type":"text","angle":0,"index":23,"text":"而后形成匹配，把目标列中重复的属性列去掉。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"75f4c889-194c-46d8-947e-5bd6c5835f26","page_size":[595,841],"block_position":"13-23"},{"bbox":[87,453,261,465],"type":"text","angle":0,"index":24,"text":"<表名 $\\uparrow > . <$ 列名 $\\gimel = { < }$ 表名 $_ { 2 > . < }$ <列名 $_ { 2 > }$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"588ba39a-f984-4ec8-82b7-28bc4be9d683","page_size":[595,841],"block_position":"13-24"},{"bbox":[87,470,95,479],"type":"text","angle":0,"index":25,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"f210343a-f7c9-452f-8e36-cff9e719a191","page_size":[595,841],"block_position":"13-25"},{"bbox":[87,484,273,497],"type":"text","angle":0,"index":26,"text":"有些 DBMS 产品，如 SQL Server，不支持","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"3b5f5beb-0ee6-47fe-832f-96026131e758","page_size":[595,841],"block_position":"13-26"},{"bbox":[87,500,311,513],"type":"text","angle":0,"index":27,"text":"NATURAL JOIN连接符，故不能直接实现自然连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"33bab9b7-de72-4cfc-b1e0-ea413015637c","page_size":[595,841],"block_position":"13-27"},{"bbox":[87,530,208,544],"type":"title","angle":0,"index":28,"text":"# 非等值连接 (Non-EquiJoin)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":13,"id":"6fa25c35-8c77-4366-97d5-b45bdd52678a","page_size":[595,841],"block_position":"13-28"},{"bbox":[87,549,95,556],"type":"text","angle":0,"index":29,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"75b120b2-b75e-43ef-b4c0-d1ac010d3e9d","page_size":[595,841],"block_position":"13-29"},{"bbox":[87,561,143,575],"type":"title","angle":0,"index":30,"text":"# 非等值连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":13,"id":"89ac1a16-1547-4ee3-acf6-df7fd539d324","page_size":[595,841],"block_position":"13-30"},{"bbox":[87,577,226,590],"type":"text","angle":0,"index":31,"text":"连接运算符不为 $=$ 的连接操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"005f3bd8-58f9-47db-bfea-2ceb503e996d","page_size":[595,841],"block_position":"13-31"},{"bbox":[87,596,95,603],"type":"text","angle":0,"index":32,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"1a189fa1-3789-41c6-8554-2b9a4456a1fe","page_size":[595,841],"block_position":"13-32"},{"bbox":[87,608,115,621],"type":"text","angle":0,"index":33,"text":"形式：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"30a6ffe9-79b1-4b10-9d17-9d9fe99c4fa5","page_size":[595,841],"block_position":"13-33"},{"bbox":[88,624,333,638],"type":"text","angle":0,"index":34,"text":"[<表名 1>.]<列名 $\\ L _ { 1 } > <$ 比较运算符 $> [ <$ <表名 $2 { > } . ] <$ <列名 $_ { 2 > }$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"588dd399-bf98-4f62-a62d-ae2367b4bc3d","page_size":[595,841],"block_position":"13-34"},{"bbox":[88,640,260,652],"type":"text","angle":0,"index":35,"text":"比较运算符： $\\therefore x _ { 1 } > = 1 < = 1 1 = ( < 2 )$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"1781229b-6878-48a2-b219-c260bfee339f","page_size":[595,841],"block_position":"13-35"},{"bbox":[87,655,311,668],"type":"text","angle":0,"index":36,"text":"[<表名 1>.]<列名 $\\Im \\succ$ BETWEEN [<表名 $2 > . ] < \\bar { \\mathcal { G } } ^ { \\mid }$ 名 $_ { 2 > }$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"80c6b86a-265b-484d-99c3-3845ef296a65","page_size":[595,841],"block_position":"13-36"},{"bbox":[87,671,198,684],"type":"text","angle":0,"index":37,"text":"AND [<表名 2>.]<列名 $\\mathfrak { 3 } \\mathfrak { > }$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"0594ae51-194a-48f9-a76b-ab164574bae6","page_size":[595,841],"block_position":"13-37"},{"bbox":[86,687,333,699],"type":"text","angle":0,"index":38,"text":"求既学过“001”号课⼜学过 “002”号课的所有学生的","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"e47032f3-b6b7-4c3f-978d-b2f974b07fb1","page_size":[595,841],"block_position":"13-38"},{"bbox":[87,702,110,714],"type":"text","angle":0,"index":39,"text":"学号","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"ecdc133d-4618-4847-af9a-b1b672820bf9","page_size":[595,841],"block_position":"13-39"},{"bbox":[87,719,116,729],"type":"text","angle":0,"index":40,"text":"Select","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"c585a31e-e6a3-4f64-89d0-6b233604b539","page_size":[595,841],"block_position":"13-40"},{"bbox":[87,734,113,744],"type":"text","angle":0,"index":41,"text":"S1.S#","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"346807ce-a6ba-49c9-8222-c40b09fbf265","page_size":[595,841],"block_position":"13-41"},{"bbox":[87,749,154,761],"type":"text","angle":0,"index":42,"text":"From SC S1, SC","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":13,"id":"e882c654-c0a6-4041-aab4-be47a9adc921","page_size":[595,841],"block_position":"13-42"}],[{"bbox":[87,79,132,89],"type":"text","angle":0,"index":0,"text":"S2 Where","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"65d95e99-1ba0-4dd2-9c15-805c9d82bb0e","page_size":[595,841],"block_position":"14-0"},{"bbox":[87,95,165,105],"type":"text","angle":0,"index":1,"text":"$\\mathsf { S } \\mathsf { 1 } . \\mathsf { S } \\# = \\mathsf { S } 2 . \\mathsf { S } \\#$ and","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"72839c6c-1e30-4956-abad-7b8311976552","page_size":[595,841],"block_position":"14-1"},{"bbox":[88,110,140,121],"type":"text","angle":0,"index":2,"text":"$\\mathsf { S } 1 . \\mathsf { C } \\# { } { } = ^ { \\iota } ( 0 0 1 ^ { \\prime }$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"9d670415-9337-4f49-a7af-33e6291aad6b","page_size":[595,841],"block_position":"14-2"},{"bbox":[88,126,107,137],"type":"text","angle":0,"index":3,"text":"and","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"22e49bfe-d606-4a45-ba40-e2c0fbb9e2dc","page_size":[595,841],"block_position":"14-3"},{"bbox":[88,141,142,153],"type":"text","angle":0,"index":4,"text":"$\\mathsf { S } 2 . \\mathsf { C } \\# = ^ { \\prime } 0 0 2$","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"823915f8-71c2-48f0-b4b0-4d2ce20c6825","page_size":[595,841],"block_position":"14-4"},{"bbox":[87,156,362,169],"type":"text","angle":0,"index":5,"text":"⽰例：求“001”号课成绩⽐“002”号课成绩⾼的所有学生的","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"464d456f-027b-49f9-973f-3e8791445050","page_size":[595,841],"block_position":"14-5"},{"bbox":[88,172,111,185],"type":"text","angle":0,"index":6,"text":"学号","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"b2f8cdb1-864f-498a-9340-6a069a8f1b0c","page_size":[595,841],"block_position":"14-6"},{"bbox":[87,188,252,200],"type":"text","angle":0,"index":7,"text":"Select S1.S# From SC S1, SC S2 Where","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"7e5ec246-cf84-4825-b0e5-fd2e53da3426","page_size":[595,841],"block_position":"14-7"},{"bbox":[88,203,218,215],"type":"text","angle":0,"index":8,"text":"$\\mathsf { S } \\mathsf { 1 } . \\mathsf { S } \\# = \\mathsf { S } 2 . \\mathsf { S } \\#$ and S1.C#=‘001’","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"19955c2b-e000-459a-b121-c7444b4f69f4","page_size":[595,841],"block_position":"14-8"},{"bbox":[88,220,107,230],"type":"text","angle":0,"index":9,"text":"and","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"9d8a708c-9076-4041-b7be-118beb354895","page_size":[595,841],"block_position":"14-9"},{"bbox":[88,235,248,247],"type":"text","angle":0,"index":10,"text":"$\\mathsf { S } 2 . \\mathsf { C } \\# { = } ^ { \\prime } 0 0 2 ^ { \\prime }$ and S1.Score $>$ S2.Score;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"dffa41d1-9ca7-4e50-a1a4-c8b967d56ecc","page_size":[595,841],"block_position":"14-10"},{"bbox":[88,251,95,260],"type":"text","angle":0,"index":11,"text":"S","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"2a1ca160-4c6b-47e9-8778-56616820619a","page_size":[595,841],"block_position":"14-11"},{"bbox":[88,265,121,279],"type":"title","angle":0,"index":12,"text":"# 外连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":14,"id":"b8551a0d-4399-404c-a66e-360499e24202","page_size":[595,841],"block_position":"14-12"},{"bbox":[88,284,95,291],"type":"text","angle":0,"index":13,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"e4885fce-f7a3-4223-b6c4-4636df2a49ec","page_size":[595,841],"block_position":"14-13"},{"bbox":[87,296,291,341],"type":"text","angle":0,"index":14,"text":"指定了OUTER关键字的为外连接，外连接的结果表不但包含满足连接条件的行，还包括相应表中的所有行。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"69a54342-ac09-4bf9-8fca-4bf8b270bed5","page_size":[595,841],"block_position":"14-14"},{"bbox":[88,346,95,354],"type":"text","angle":0,"index":15,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"a7c85cdd-f415-4b34-8c4c-e58e3409e732","page_size":[595,841],"block_position":"14-15"},{"bbox":[87,359,289,403],"type":"text","angle":0,"index":16,"text":"外连接中，可以只限制一个表，而对另一个表不加限制（即所有的行都出现在结果集中）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"9b8c524a-dbf7-430d-925f-8f9ae3116d6f","page_size":[595,841],"block_position":"14-16"},{"bbox":[88,408,95,416],"type":"text","angle":0,"index":17,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"0c4f675a-dd9e-4f5b-9cad-71b1f4301566","page_size":[595,841],"block_position":"14-17"},{"bbox":[87,421,293,434],"type":"text","angle":0,"index":18,"text":"外连接分为左外连接、右外连接和全外连接。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"a6a840f3-76a5-4b80-9ab8-3cef98dcfe5f","page_size":[595,841],"block_position":"14-18"},{"bbox":[88,453,174,466],"type":"title","angle":0,"index":19,"text":"# 自身连接(Self-Join)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":14,"id":"e739ca60-8fb4-4d2c-a04b-82fa872916b6","page_size":[595,841],"block_position":"14-19"},{"bbox":[88,470,95,479],"type":"text","angle":0,"index":20,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"1e59f0e1-7125-4136-bf3d-faf6ed29c13d","page_size":[595,841],"block_position":"14-20"},{"bbox":[87,483,373,513],"type":"text","angle":0,"index":21,"text":"连接操作是在同一张表内进行自身连接，即将同一个表的不同行连接起来。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"ab7269b2-327d-4334-a5a1-64061d6263a4","page_size":[595,841],"block_position":"14-21"},{"bbox":[88,518,95,525],"type":"text","angle":0,"index":22,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"ab209325-19e2-4455-b801-9f9b237db687","page_size":[595,841],"block_position":"14-22"},{"bbox":[88,530,283,544],"type":"text","angle":0,"index":23,"text":"可看作一张表的两个副本之间进行的连接。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"896b83bf-0f25-4c60-affc-9c32fe6686fd","page_size":[595,841],"block_position":"14-23"},{"bbox":[88,549,95,556],"type":"text","angle":0,"index":24,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"75961630-ed6b-4b12-ad95-b7768e19cf91","page_size":[595,841],"block_position":"14-24"},{"bbox":[87,561,325,575],"type":"text","angle":0,"index":25,"text":"必须为表指定两个别名，使之在逻辑上成为两张表。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"83ed3f5b-c6d4-4c7f-bce4-99a409da5b1b","page_size":[595,841],"block_position":"14-25"},{"bbox":[88,580,95,588],"type":"text","angle":0,"index":26,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"295dbab9-181b-42a8-84b4-771e30828d1a","page_size":[595,841],"block_position":"14-26"},{"bbox":[88,593,342,618],"type":"text","angle":0,"index":27,"text":"由于所有属性名都是同名属性，因此必须使用别名前缀v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"00ff6f89-1afd-4db2-a12a-345ca67d72ba","page_size":[595,841],"block_position":"14-27"},{"bbox":[88,624,271,637],"type":"text","angle":0,"index":28,"text":"例 36.查询 Employee 表中的同姓的职工。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"1e9f1e9f-f17e-450b-86dc-414f5c580120","page_size":[595,841],"block_position":"14-28"},{"bbox":[88,640,210,651],"type":"text","angle":0,"index":29,"text":"SELECT e1.Ename,e2.Ename","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"dfaff92c-e013-4548-ad57-880d7d1382ae","page_size":[595,841],"block_position":"14-29"},{"bbox":[88,655,255,667],"type":"text","angle":0,"index":30,"text":"FROM Employee e1 JOIN Employee e2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"8886c3e1-9c5b-4ef3-beff-37019912dc3f","page_size":[595,841],"block_position":"14-30"},{"bbox":[88,671,252,683],"type":"text","angle":0,"index":31,"text":"ON left(e1.Ename,1)=left(e2.Ename,1)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":14,"id":"65cc2873-be7e-4490-a119-18987111e85a","page_size":[595,841],"block_position":"14-31"},{"bbox":[88,687,188,698],"type":"text","angle":0,"index":32,"text":"WHERE e1.EnoAVG(Age);","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":16,"id":"cb95f08d-7c31-46e0-ab4b-c88efe065403","page_size":[595,841],"block_position":"16-1"},{"bbox":[87,110,143,123],"type":"title","angle":0,"index":2,"text":"# 相关子查询","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":16,"id":"cebe4d8f-e4be-4a10-b216-ed8b3a6af08a","page_size":[595,841],"block_position":"16-2"},{"bbox":[87,127,96,137],"type":"text","angle":0,"index":3,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":16,"id":"e526056a-b7ab-4748-9d72-dd7ab97c16e9","page_size":[595,841],"block_position":"16-3"},{"bbox":[86,141,290,170],"type":"text","angle":0,"index":4,"text":"执行依赖于外部查询，多数情况下是在子查询的WHERE子句中引用了外部查询的表。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":16,"id":"08b1e3c7-aa78-4c64-bde9-49bd3695502d","page_size":[595,841],"block_position":"16-4"},{"bbox":[87,174,96,184],"type":"text","angle":0,"index":5,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":16,"id":"6f93bb71-7bf7-4a6f-a3d2-7f9ebfaf3abc","page_size":[595,841],"block_position":"16-5"},{"bbox":[86,187,290,216],"type":"text","angle":0,"index":6,"text":"可以使用EXISTS关键字来判断查询结果中是否存在数据，EXISTS在一个子查询至少返回","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":16,"id":"e1df1a62-e74d-4553-8c06-6b3387fb3346","page_size":[595,841],"block_position":"16-6"},{"bbox":[87,219,147,232],"type":"text","angle":0,"index":7,"text":"一行时成立。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":16,"id":"37926ef4-82dc-4344-9257-953a9e26769b","page_size":[595,841],"block_position":"16-7"},{"bbox":[90,231,595,572],"index":8,"angle":0,"type":"image","img_path":"/9befa48b9bdf61690405bec38c2b72f386915c759717198cd755efd254411539.jpg","color":{"line":"rgba(89, 92, 220, 1)","fill":"rgba(89, 92, 220, 1)"},"img_ratio":0.8487394957983193,"page_idx":16,"id":"f75b8b9e-a7bd-42c5-b923-a848544da7d7","page_size":[595,841],"block_position":"16-8"}],[{"bbox":[328,143,536,187],"type":"title","angle":0,"index":0,"text":"# 索引的概念","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":17,"id":"a59244fa-965e-46b1-862f-ba4979296ac2","page_size":[595,841],"block_position":"17-0"},{"bbox":[161,198,595,260],"type":"text","angle":0,"index":1,"text":"索引是定义在基本表(Table)基础之上，有助于无需检查所有记录位所需记录的一种辅助存储结构，由一系列存储在磁盘上的索引项entries)组成，每一索引项又由两部分构成：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"73e1e7fa-14f1-4736-b94a-fb14121429b4","page_size":[595,841],"block_position":"17-1"},{"bbox":[161,264,595,304],"type":"text","angle":0,"index":2,"text":"√索引字段：由Table中某些列(通常是一列)中的值串接而成。索引索引字段的每一个值(也有不是这样的)。索引字段类似于词典中的词条。","id":"b1b5f4a3-8ec1-498d-b470-e91d51167277","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"page_size":[595,841],"block_position":"17-2"},{"bbox":[161,310,595,352],"type":"text","angle":0,"index":3,"text":"√行指针：指向Table中包含索引字段值的记录在磁盘上的存储位条在书籍、词典中出现的页码。","id":"133fbcb8-bde4-4cf9-a55e-048bbcd898a7","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"page_size":[595,841],"block_position":"17-3"},{"bbox":[162,359,595,380],"type":"text","angle":0,"index":4,"text":"·存储索引项的文件为索引文件，相对应，基本表又称为主文","id":"3aff663c-2145-41f4-97a9-059c52ea8562","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"page_size":[595,841],"block_position":"17-4"},{"bbox":[205,408,370,428],"type":"text","angle":0,"index":6,"text":"Index-field pointer","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"fcc3682f-6af1-4959-8fe4-2c279a7393ea","page_size":[595,841],"block_position":"17-5"},{"bbox":[214,485,264,528],"type":"title","angle":0,"index":7,"text":"# Index索引文","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":17,"id":"f3860429-313b-4065-adda-032261090df2","page_size":[595,841],"block_position":"17-6"},{"bbox":[268,437,595,528],"index":8,"angle":0,"type":"table_body","img_path":"/","id":"f7ea4bd0-0667-4b6f-a9e3-199babbd7ebb","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
Course
C#C#ChameChoursCreditT
001001数据库4060
002003数据结构4060
003004编译原理4060
004005C语言304.50
005002高等数学80120
006006计算机原理4060
007009数理逻辑4060
008008组合数学304.50
","page_idx":17,"page_size":[595,841],"block_position":"17-7"},{"bbox":[86,530,149,544],"type":"title","angle":0,"index":9,"text":"# 4.3 数据修改","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":17,"id":"0621a39f-4ee1-4f30-a59c-940c8e3cd4b1","page_size":[595,841],"block_position":"17-8"},{"bbox":[87,546,248,560],"type":"text","angle":0,"index":10,"text":"考核要求：达到“综合应用”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"f6948d44-2db3-4fa1-8999-f0aead991cb2","page_size":[595,841],"block_position":"17-9"},{"bbox":[86,577,168,590],"type":"text","angle":0,"index":11,"text":"UPDATE 基本表名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"6e7a0d2e-a6b1-4e9c-8bab-f926a607fe86","page_size":[595,841],"block_position":"17-10"},{"bbox":[86,593,261,607],"type":"text","angle":0,"index":12,"text":"SET 列名 $=$ 值表达式,[列名 $=$ 值表达式...]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"c8f1cfa4-b93f-4598-8247-d11e0cd6d07a","page_size":[595,841],"block_position":"17-11"},{"bbox":[87,608,183,622],"type":"text","angle":0,"index":13,"text":"[WHERE 条件表达式]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"fcf440de-47a9-4c93-85e4-380bd6a0f039","page_size":[595,841],"block_position":"17-12"},{"bbox":[86,624,505,653],"type":"text","angle":0,"index":14,"text":"(语义：修改基本表中满足条件表达式的那些元组中的列值，需修改的列值在 SET子句中指出）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"0ec5bc75-78c5-440a-a6f4-dee769773abb","page_size":[595,841],"block_position":"17-13"},{"bbox":[87,655,206,668],"type":"text","angle":0,"index":15,"text":"注意带子查询的数据更新","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"6cbb6766-2d0a-4cef-b3d3-3d46f7f94f9e","page_size":[595,841],"block_position":"17-14"},{"bbox":[87,687,158,699],"type":"text","angle":0,"index":16,"text":"(1)视图的创建：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"012c8039-0ada-4634-b793-4343f36ffe45","page_size":[595,841],"block_position":"17-15"},{"bbox":[87,702,309,715],"type":"text","angle":0,"index":17,"text":"CREATE VIEW 视图名(列名表) AS SELECT 查询语句","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"8fd0c5a2-2bfe-40af-9185-abae560eede7","page_size":[595,841],"block_position":"17-16"},{"bbox":[88,717,158,730],"type":"text","angle":0,"index":18,"text":"(2)视图的撤消：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"8b3e2932-8caf-4d1c-bec1-705486b55cd6","page_size":[595,841],"block_position":"17-17"},{"bbox":[87,734,173,746],"type":"text","angle":0,"index":19,"text":"DROP VIEW 视图名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"c1f23c7c-1042-453c-972f-f95a6ddee03f","page_size":[595,841],"block_position":"17-18"},{"bbox":[90,749,135,761],"type":"text","angle":0,"index":20,"text":"语句格式","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":17,"id":"e6f91d1f-cbe3-4b4b-8b29-31250605a337","page_size":[595,841],"block_position":"17-19"}],[{"bbox":[86,79,254,92],"type":"text","angle":0,"index":0,"text":"CREATE VIEW <视图名> [<列名清单>]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"4d9e55fd-418d-4d3d-b262-e4fa09a6137c","page_size":[595,841],"block_position":"18-0"},{"bbox":[87,95,145,107],"type":"text","angle":0,"index":1,"text":"AS <子查询>","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"3beb766a-eecf-4ab7-b84f-6a5bc0da7e91","page_size":[595,841],"block_position":"18-1"},{"bbox":[87,110,189,122],"type":"text","angle":0,"index":2,"text":"[WITH CHECK OPTION]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"95cf1403-cbdd-4889-868f-96ff1797d768","page_size":[595,841],"block_position":"18-2"},{"bbox":[88,128,95,136],"type":"text","angle":0,"index":3,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"0ee54e41-2b7d-48f3-a860-bede4b169cf0","page_size":[595,841],"block_position":"18-3"},{"bbox":[88,141,111,153],"type":"title","angle":0,"index":4,"text":"# 说明","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":18,"id":"da6640f1-d9a6-4210-bbee-2e9d710f7e0e","page_size":[595,841],"block_position":"18-4"},{"bbox":[89,157,254,169],"type":"text","angle":0,"index":5,"text":"<视图名 $>$ 给出所定义的视图的名称。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"0d855d85-1b0b-40ce-b7f6-3c9e151fae46","page_size":[595,841],"block_position":"18-5"},{"bbox":[88,172,411,184],"type":"text","angle":0,"index":6,"text":"<列名清单>，若有则此清单给出了此视图的全部属性的属性名；否则，","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"3b553b0b-7d6a-40d6-ad6a-8a96ed6549bb","page_size":[595,841],"block_position":"18-6"},{"bbox":[87,188,380,200],"type":"text","angle":0,"index":7,"text":"此视图的所有属性名即为子查询中 SELECT 语句中的全部目标列。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"2d579b8e-d70c-401b-b12c-afb18979c21f","page_size":[595,841],"block_position":"18-7"},{"bbox":[88,203,365,216],"type":"text","angle":0,"index":8,"text":"<子查询>为任一合法 SELECT 语句（但一般不含有 ORDER BY，","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"4481ab8f-dbde-491f-bcc3-f887b600e15b","page_size":[595,841],"block_position":"18-8"},{"bbox":[87,220,189,232],"type":"text","angle":0,"index":9,"text":"UNION 等语法成分）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"507d6520-97c8-4af3-bf99-3964016e8337","page_size":[595,841],"block_position":"18-9"},{"bbox":[88,235,351,247],"type":"text","angle":0,"index":10,"text":"有[WITH CHECK OPTION]时，则今后对此视图进行 INSERT、","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"b90da3a6-40fa-4f2f-bcd2-eb35da7a4ab0","page_size":[595,841],"block_position":"18-10"},{"bbox":[87,250,392,262],"type":"text","angle":0,"index":11,"text":"UPDATE和DELETE操作时，系统自动检查是否符合原定义视图子查","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"31b2b6c1-2121-4c2e-9b69-aa67934fa0dd","page_size":[595,841],"block_position":"18-11"},{"bbox":[87,266,188,279],"type":"text","angle":0,"index":12,"text":"询中的<条件表达式>。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"b609d25d-5354-49e7-9633-8788d61502b8","page_size":[595,841],"block_position":"18-12"},{"bbox":[87,281,166,294],"type":"title","angle":0,"index":13,"text":"# 4.4.2 视图的更新","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":18,"id":"cb6492d4-1804-4942-877e-a21f1013ddc8","page_size":[595,841],"block_position":"18-13"},{"bbox":[86,296,509,310],"type":"text","angle":0,"index":14,"text":"对视图的查询(SELECT)操作，和基本表一样，但是视图的更新操作受到下列三条规则的限制：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"93c3661c-593f-42d2-9f0c-c16f566165d2","page_size":[595,841],"block_position":"18-14"},{"bbox":[104,328,414,341],"type":"text","angle":0,"index":15,"text":"如果视图是从多个基本表使用连接操作导出的，则不允许更新。","id":"d965a9f8-4ede-4b8b-8f58-66a287095022","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-15"},{"bbox":[104,343,381,356],"type":"text","angle":0,"index":16,"text":"如果导出的视图使用了分组和聚合操作，也不允许更新。","id":"4c6897b3-7db4-4da2-be5c-f059bc0d0e38","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-16"},{"bbox":[86,359,504,387],"type":"text","angle":0,"index":18,"text":"如果视图是从单个基本表使用选择、投影操作导出的，并且包括了基本表的主键和没有缺省值的不可为空的列， 那么这样的视图称为“行列子集视图”，则可以执行操作。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"ffc66198-9496-49cb-86db-2130b050fe2c","page_size":[595,841],"block_position":"18-17"},{"bbox":[86,390,504,418],"type":"text","angle":0,"index":19,"text":"有些查询使用一个Select语句完成，可能做不到（也可能是逻辑上太绕），可以使用视图存放中间查询的数据，在后续Select语句中跟视图进行连接查询实现。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"166cda80-5f28-4ccf-b7d0-4eca29968936","page_size":[595,841],"block_position":"18-18"},{"bbox":[87,422,397,434],"type":"text","angle":0,"index":20,"text":"数据库完整性是通过 DBMS 的完整性子系统实现的，它有两个功能：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"8d56c275-f9ea-42d1-9f98-de20eb315659","page_size":[595,841],"block_position":"18-19"},{"bbox":[86,453,315,465],"type":"text","angle":0,"index":21,"text":"(1)监督事务的执行，并测试是否违反完整性规则。","id":"1072b25c-720f-44b5-b316-a02fb9466006","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-20"},{"bbox":[86,468,483,481],"type":"text","angle":0,"index":22,"text":"(2)如有违反，则采取恰当的操作，如拒绝、报告违反情况，改正错误等方法进行处理。","id":"fb143b3f-8aa1-44d9-9f94-868eba908c0e","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-21"},{"bbox":[87,484,227,497],"type":"text","angle":0,"index":24,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"036ce607-c1d6-4fbc-b175-7d92addc7752","page_size":[595,841],"block_position":"18-22"},{"bbox":[87,500,236,512],"type":"text","angle":0,"index":25,"text":"知识点：规则的组成部分及分类","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"90489fe6-1dad-4458-b1a8-5f12be2091c1","page_size":[595,841],"block_position":"18-23"},{"bbox":[86,530,338,544],"type":"text","angle":0,"index":26,"text":"数据库完整性子系统是根据“完整性规则集” 工作的，","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"a815cf8d-f21b-431c-8cfa-221e9656fddf","page_size":[595,841],"block_position":"18-24"},{"bbox":[86,546,504,575],"type":"text","angle":0,"index":27,"text":"完整性规则是由数据库管理员或应用程序员事先向完整性子系统提供有关数据约束的一组规则。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"4b8e93dd-c6c5-42e6-a3ca-1e5c33d865cd","page_size":[595,841],"block_position":"18-25"},{"bbox":[87,593,157,605],"type":"title","angle":0,"index":28,"text":"# 由三部分组成：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":18,"id":"3242e5e2-8143-412e-b61b-c60486919f1d","page_size":[595,841],"block_position":"18-26"},{"bbox":[94,608,246,621],"type":"text","angle":0,"index":29,"text":"（1）什么时候使用规则进行检查；","id":"70f9ad2e-3746-4ebb-b1b9-497cb0881cc9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-27"},{"bbox":[94,624,215,637],"type":"text","angle":0,"index":30,"text":"（2）要检查什么样的错误；","id":"e32b4e2a-a55f-43a6-a650-75f2b6353cad","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-28"},{"bbox":[94,640,246,652],"type":"text","angle":0,"index":31,"text":"（3）若检查出错误，该怎样处理。","id":"f8abe562-5852-48a1-a26e-ad92c4e5a783","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-29"},{"bbox":[86,671,304,683],"type":"text","angle":0,"index":33,"text":"在关系数据库中，这些完整性规则可分为三类：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"6bd3f37a-cbaf-4d2e-a2a9-7ec5c7c08e4f","page_size":[595,841],"block_position":"18-30"},{"bbox":[96,687,192,699],"type":"text","angle":0,"index":34,"text":"（1）用户定义完整性","id":"6b715a86-30d1-4408-a9f4-bb37c8be318a","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-31"},{"bbox":[96,702,171,714],"type":"text","angle":0,"index":35,"text":"（2）实体完整性","id":"e7d92ee1-fae7-42e1-9053-3ea4a69f908c","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-32"},{"bbox":[96,718,171,730],"type":"text","angle":0,"index":36,"text":"（3）参照完整性","id":"1facaf93-24f9-4dbb-9658-4a62733ce9d6","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"page_size":[595,841],"block_position":"18-33"},{"bbox":[87,734,309,746],"type":"text","angle":0,"index":38,"text":"1）主码约束：可用主码子句或主码短语来定义。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"6581012b-a93f-4055-a311-ecf611434547","page_size":[595,841],"block_position":"18-34"},{"bbox":[87,750,229,761],"type":"text","angle":0,"index":39,"text":"如 PRIMARY KEY (S#) (主码子句)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":18,"id":"9f741bd8-c3f0-433d-97b1-4f5a0a3fbccd","page_size":[595,841],"block_position":"18-35"}],[{"bbox":[87,79,354,92],"type":"header","angle":0,"index":-99999,"text":"S# CHAR (4) PRIMARY KEY (其中，PRIMARY KEY 为主码短语）","color":{"line":"rgba(164, 164, 164, 1)","fill":"rgba(164, 164, 164, 1)"},"page_idx":19,"is_discarded":true,"id":"08daf498-acf7-4f71-9dec-6fbfc534c7b1","page_size":[595,841],"block_position":"19-0"},{"bbox":[94,110,263,122],"type":"title","angle":0,"index":1,"text":"# （2）外码约束：可用外码子句来定义","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":19,"id":"707e40f6-307d-48dd-87fc-d3285399ed7d","page_size":[595,841],"block_position":"19-1"},{"bbox":[102,126,262,138],"type":"text","angle":0,"index":2,"text":"如 FOREIGN KEY (S#) REFERNCE S(S#)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"22b03baf-2f5b-493e-8219-307940259b55","page_size":[595,841],"block_position":"19-2"},{"bbox":[96,138,411,224],"index":3,"angle":0,"type":"table_body","img_path":"/","id":"3707052c-9f9e-4a07-af18-4c46dc85f2d1","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
删除基本关系元组时的考虑外码子句加"ON DELETE"短语
修改基本关系中主码值的考虑外码子句加"ON UPDATE"短语
三种方式：NO ACTION, RESTRICT, CASCADE, SET NULL (具体含义)
","page_idx":19,"page_size":[595,841],"block_position":"19-3"},{"bbox":[93,226,449,239],"type":"text","angle":0,"index":4,"text":"（3）属性值约束：包括非空值约束(NOT NULL)；基于属性的检查子句(CHECK) ；","id":"108e7a77-0157-494f-89fb-158f3aa58672","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"page_size":[595,841],"block_position":"19-4"},{"bbox":[94,241,319,254],"type":"text","angle":0,"index":5,"text":"（4）全局约束：包括基于元组的检查子句(CHECK)","id":"340e6e3b-8cd6-41e0-854e-93c77179e822","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"page_size":[595,841],"block_position":"19-5"},{"bbox":[88,257,462,270],"type":"text","angle":0,"index":7,"text":"$\\star$ 在 employee 中插入记录，其 dno 值 not null， 但不在 department (dno) 中出现；","id":"9885e2aa-2142-4e6c-96d8-590d929419ab","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"page_size":[595,841],"block_position":"19-6"},{"bbox":[89,272,452,286],"type":"text","angle":0,"index":8,"text":"$\\star$ 修改 employee 的记录，新 dno 值 not null， 但不在 department (dno) 中出现；","id":"fd692661-2ce9-4eb2-8dbd-6c60df8f6fa2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"page_size":[595,841],"block_position":"19-7"},{"bbox":[89,288,413,301],"type":"text","angle":0,"index":9,"text":"$\\star$ 删除 department 的记录，但相应的 dno 值出现在 employee (dno) 中；","id":"1c02e5b3-fee7-4cb7-a026-d16a6b582eae","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"page_size":[595,841],"block_position":"19-8"},{"bbox":[89,303,413,317],"type":"text","angle":0,"index":10,"text":"$\\star$ 修改 department 中的记录，但旧的 dno 值出现在 employee (dno) 中。","id":"02dce93c-9907-4fbd-84a7-e617304e96ef","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"page_size":[595,841],"block_position":"19-9"},{"bbox":[87,319,283,332],"type":"text","angle":0,"index":12,"text":"Restrict（限制策略） ——SQL 的默认策略，","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"86dc3b56-c641-4b94-ae15-fc1a8a02d62f","page_size":[595,841],"block_position":"19-10"},{"bbox":[87,334,179,348],"type":"text","angle":0,"index":13,"text":"针对以上四种情况；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"5ac9c50e-cde6-4ec8-8503-63250def4955","page_size":[595,841],"block_position":"19-11"},{"bbox":[88,351,98,360],"type":"text","angle":0,"index":14,"text":"","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"40fa5aea-2c21-4700-b339-32f1b18c4a14","page_size":[595,841],"block_position":"19-12"},{"bbox":[87,365,308,379],"type":"text","angle":0,"index":15,"text":"Cascade（级联策略）——针对以上后两种情况；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"839b5e8d-d54f-4236-a9af-1fcab9ecd262","page_size":[595,841],"block_position":"19-13"},{"bbox":[88,382,98,391],"type":"text","angle":0,"index":16,"text":"","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"014951e7-35ea-47e8-970c-f3d6fb4577f5","page_size":[595,841],"block_position":"19-14"},{"bbox":[87,396,307,410],"type":"text","angle":0,"index":17,"text":"Set Null（置空策略）——针对以上后两种情况。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"a4a549e4-80e0-4c1a-a52f-f3815f330337","page_size":[595,841],"block_position":"19-15"},{"bbox":[88,412,98,422],"type":"text","angle":0,"index":18,"text":"","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"dfee477b-2fbe-48d7-890b-a8c2a20fbe25","page_size":[595,841],"block_position":"19-16"},{"bbox":[87,428,277,441],"type":"title","angle":0,"index":19,"text":"# 三种策略有 On Delete , On Update 可供选","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":19,"id":"036ed437-55fa-461e-94fe-162432d16a4e","page_size":[595,841],"block_position":"19-17"},{"bbox":[87,444,237,456],"type":"text","angle":0,"index":20,"text":"对约束的命名、撤消和添加操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"4c39837f-010b-465a-81fd-5ee423801d74","page_size":[595,841],"block_position":"19-18"},{"bbox":[94,460,168,472],"type":"text","angle":0,"index":21,"text":"（1）约束的命名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"ac4d440a-54ea-4531-8442-e6f0aed622f9","page_size":[595,841],"block_position":"19-19"},{"bbox":[92,475,343,487],"type":"text","angle":0,"index":22,"text":"在定义时，前面加上关键字CONSTRACT和约束名即可。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"27bc5c94-29d8-4f02-8091-af97980f8625","page_size":[595,841],"block_position":"19-20"},{"bbox":[94,491,242,503],"type":"text","angle":0,"index":23,"text":"（2）在关系上约束的撤消与添加","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"3a0440bd-2c6c-4f78-be5e-c920b60fbb16","page_size":[595,841],"block_position":"19-21"},{"bbox":[94,506,504,534],"type":"text","angle":0,"index":24,"text":"在 关 系 定义中 ，撤消约 束 用 “ALTER TABLE ...DROP CONSTRAINT...”语 句 ，添加约 束 用“ALTER TABLE ...ADD CONSTRAINT ...”语句","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"2c66aaa9-f1fd-422c-abf8-f5938961719c","page_size":[595,841],"block_position":"19-22"},{"bbox":[88,537,153,550],"type":"text","angle":0,"index":25,"text":" Check 约束：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"0c7432a3-a39f-4c2a-91f1-e047f6ab7e9b","page_size":[595,841],"block_position":"19-23"},{"bbox":[88,553,294,565],"type":"text","angle":0,"index":26,"text":"$\\star$ 约束条件可以是任何 Where 中出现的字句；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"be504e84-6ba3-4fab-af57-a812d05c7078","page_size":[595,841],"block_position":"19-24"},{"bbox":[88,568,199,581],"type":"text","angle":0,"index":27,"text":"故具有很强的表述能力；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"ddb9256c-9387-4c95-9670-d1914d80a456","page_size":[595,841],"block_position":"19-25"},{"bbox":[88,584,209,597],"type":"text","angle":0,"index":28,"text":"$\\star$ 常用于数据的值域约束；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"863880a8-ad38-4e26-a48e-98f9effa0327","page_size":[595,841],"block_position":"19-26"},{"bbox":[88,601,293,613],"type":"text","angle":0,"index":29,"text":"三、User Defined Integrity and Default、Check","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"74919af2-f075-4262-a409-d496454f4d8f","page_size":[595,841],"block_position":"19-27"},{"bbox":[88,616,170,628],"type":"text","angle":0,"index":30,"text":"Col_constr 列约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"bd69aca6-7cc2-4335-8c83-f6979fbfa6db","page_size":[595,841],"block_position":"19-28"},{"bbox":[88,630,287,644],"type":"text","angle":0,"index":31,"text":"一种域约束类型，对单一列的值进行约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"e9280fc0-b0c5-40d2-9902-b26ba0c2f6db","page_size":[595,841],"block_position":"19-29"},{"bbox":[88,646,146,658],"type":"text","angle":0,"index":32,"text":"{ NOT NULL |","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"8dff8ddd-b7ab-4a95-8494-54541cc9b23a","page_size":[595,841],"block_position":"19-30"},{"bbox":[88,661,229,674],"type":"text","angle":0,"index":33,"text":"[ CONSTRAINT constraintname ]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"07280661-6959-41e2-8b0b-e94ddf771af3","page_size":[595,841],"block_position":"19-31"},{"bbox":[88,677,132,689],"type":"text","angle":0,"index":34,"text":"{ UNIQUE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"fd02b4b4-9a2a-4a5f-94a9-85431e503a71","page_size":[595,841],"block_position":"19-32"},{"bbox":[88,693,157,704],"type":"text","angle":0,"index":35,"text":"| PRIMARY KEY","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"9ab6cfb0-297d-4b6e-9ea9-c258d0a742e1","page_size":[595,841],"block_position":"19-33"},{"bbox":[89,708,126,720],"type":"text","angle":0,"index":36,"text":"| CHECK","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"8e97a372-d087-4361-b20b-ca951b975db4","page_size":[595,841],"block_position":"19-34"},{"bbox":[88,724,151,736],"type":"text","angle":0,"index":37,"text":"(search_cond)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"264435dd-0b2f-405e-a5d8-a63cbf6facae","page_size":[595,841],"block_position":"19-35"},{"bbox":[88,740,140,752],"type":"text","angle":0,"index":38,"text":"//列值非空","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":19,"id":"7c02e9e4-4782-456b-8523-3777d50ad050","page_size":[595,841],"block_position":"19-36"}],[{"bbox":[86,79,224,91],"type":"text","angle":0,"index":0,"text":"//为约束命名，便于以后撤消","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"93e40bd5-9bc3-416c-b0eb-adf3613f28bc","page_size":[595,841],"block_position":"20-0"},{"bbox":[87,95,151,106],"type":"text","angle":0,"index":1,"text":"//列值是唯一","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"f208160b-d1b0-4aa4-a125-88842ffa1d13","page_size":[595,841],"block_position":"20-1"},{"bbox":[87,110,141,122],"type":"text","angle":0,"index":2,"text":"//列为主键","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"dce50992-e882-4064-9c43-ef50c1691d86","page_size":[595,841],"block_position":"20-2"},{"bbox":[86,125,258,138],"type":"text","angle":0,"index":3,"text":"//列值满足条件,条件只能使用列当前","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"62c25943-2705-428e-8f05-6a32740488ef","page_size":[595,841],"block_position":"20-3"},{"bbox":[87,142,101,153],"type":"text","angle":0,"index":4,"text":"值","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"7477a0eb-4174-48be-ae09-a165e271e66c","page_size":[595,841],"block_position":"20-4"},{"bbox":[88,156,256,169],"type":"text","angle":0,"index":5,"text":"| REFERENCES tablename [(colname) ]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"ffa3626a-3fec-4bc2-a9b9-03b60125d4a4","page_size":[595,841],"block_position":"20-5"},{"bbox":[88,172,252,185],"type":"text","angle":0,"index":6,"text":"[ON DELETE { CASCADE | SET NULL } ]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"8148306b-843c-4861-ae34-27babf24ae18","page_size":[595,841],"block_position":"20-6"},{"bbox":[86,203,446,248],"type":"text","angle":0,"index":8,"text":"//引用另一表 tablename 的列 colname 的值，如有 ON DELETE CASCADE 或 ONDELETE SET NULL语句，则删除被引用表的某列值v 时，要将本表该列值为 $\\mathsf { v }$ 的记录删除或列值更新为 null；缺省为无操作 。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"b3751026-be80-470f-b6f8-b06e0f8279de","page_size":[595,841],"block_position":"20-7"},{"bbox":[87,250,370,263],"type":"text","angle":0,"index":9,"text":" Col_constr 列约束：只能应用在单一列上，其后面的约束如","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"c1a1e4f3-3b9f-43a4-8898-16b64eb809e2","page_size":[595,841],"block_position":"20-8"},{"bbox":[86,266,351,279],"type":"text","angle":0,"index":10,"text":"UNIQUE, PRIMARY KEY 及 search_cond 只能是单一列唯一、","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"a6324aca-ca6a-4758-9569-aff52cd37cc4","page_size":[595,841],"block_position":"20-9"},{"bbox":[87,281,206,294],"type":"text","angle":0,"index":11,"text":"单一列为主键、和单一列","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"1a8c6718-f1a7-4cd0-b206-5021cd7f30d2","page_size":[595,841],"block_position":"20-10"},{"bbox":[88,297,111,309],"type":"text","angle":0,"index":12,"text":"相关","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"ac1a0bfa-34bf-4084-9e33-ef08076a1cfc","page_size":[595,841],"block_position":"20-11"},{"bbox":[93,317,193,333],"type":"title","angle":0,"index":13,"text":"# Col_constr列约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":20,"id":"a39a9a02-3012-4105-b057-ba984b428cf7","page_size":[595,841],"block_position":"20-12"},{"bbox":[93,336,262,348],"type":"text","angle":0,"index":14,"text":"》一种域约束类型，对单一列的值进行约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"215e6828-4ecd-43b0-a5cd-9d257914514c","page_size":[595,841],"block_position":"20-13"},{"bbox":[93,349,151,361],"type":"text","angle":0,"index":15,"text":"{ NOT NULL |","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"c7cdc9c6-6a7a-43d5-b903-92f850c265e7","page_size":[595,841],"block_position":"20-14"},{"bbox":[94,363,232,375],"type":"text","angle":0,"index":17,"text":"[ CONSTRAINT constraintname ]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"3adb38ae-28fb-475b-a34c-85d51d680aff","page_size":[595,841],"block_position":"20-15"},{"bbox":[94,377,139,387],"type":"text","angle":0,"index":19,"text":"{UNIQUE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"919d3619-71a8-45f8-8753-4188873b3de5","page_size":[595,841],"block_position":"20-16"},{"bbox":[94,391,161,401],"type":"text","angle":0,"index":21,"text":"PRIMARY KEY","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"a25abcb2-ecea-405c-9acd-a603c0061c27","page_size":[595,841],"block_position":"20-17"},{"bbox":[94,404,132,415],"type":"text","angle":0,"index":23,"text":"|CHECK","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"76c40bb5-5a54-4b7c-b2e4-8c698aa00092","page_size":[595,841],"block_position":"20-18"},{"bbox":[165,405,227,416],"type":"text","angle":0,"index":24,"text":"(search_cond)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"33a3b3b1-ae3c-4d34-ac40-8796e0b782fa","page_size":[595,841],"block_position":"20-19"},{"bbox":[155,418,332,430],"type":"text","angle":0,"index":27,"text":"| REFERENCES tablename [(colname)]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"2e29a74c-2f61-4d64-8417-2e43fe576026","page_size":[595,841],"block_position":"20-20"},{"bbox":[155,432,362,444],"type":"text","angle":0,"index":29,"text":"[ON DELETE{CASCADE| SET NULL}]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"b05a04ae-d07e-416a-b885-74413ca1b0cb","page_size":[595,841],"block_position":"20-21"},{"bbox":[154,444,399,473],"type":"text","angle":0,"index":30,"text":"//引用另一表tablename的列colname的值，如有ONDELETECASCADE或ONDELETESETNULL语句，则删除被引用表的某列值y时，要将本表该列值为y的记录删除或列值更新为null：缺省为无操作。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"70d21721-a213-4156-927a-9c02d238854a","page_size":[595,841],"block_position":"20-22"},{"bbox":[154,474,397,508],"type":"text","angle":0,"index":31,"text":"$\\gtrdot$ Col_constr列约束：只能应用在单一列上，其后面的约束如UNIQUE，PRIMARYKEY及search_cond只能是单一列唯一、单一列为主键、和单一列","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"67ded534-0962-42d8-87fd-d6df3bee5d95","page_size":[595,841],"block_position":"20-23"},{"bbox":[155,510,174,521],"type":"text","angle":0,"index":32,"text":"相关","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"0e90cc72-77c3-4db3-93d7-6159e35765ce","page_size":[595,841],"block_position":"20-24"},{"bbox":[97,547,143,556],"type":"text","angle":0,"index":33,"text":"Create Table","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"e357389e-ba20-438f-be5d-97886e7b2d2f","page_size":[595,841],"block_position":"20-25"},{"bbox":[165,548,208,556],"type":"text","angle":0,"index":34,"text":"Student (S#","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"337ae89d-4c81-412d-818c-fe95b88d1dbe","page_size":[595,841],"block_position":"20-26"},{"bbox":[233,548,342,556],"type":"text","angle":0,"index":35,"text":"char(8) not null unique, Sname","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"28279b3c-ca0c-422f-9848-d937a9662030","page_size":[595,841],"block_position":"20-27"},{"bbox":[97,559,357,568],"type":"text","angle":0,"index":36,"text":"char(10), Ssex char(2) constraint ctssex check (Ssex= ‘男’or Ssex=‘女","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"29d72f61-b6cf-48ac-a4e8-df1d5977b118","page_size":[595,841],"block_position":"20-28"},{"bbox":[131,570,302,579],"type":"text","angle":0,"index":38,"text":" Sage integer check (Sage>=1 and Sage<150), D#","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"d98ab900-2957-4036-8f81-0eaf2db2bc11","page_size":[595,841],"block_position":"20-29"},{"bbox":[131,581,295,590],"type":"text","angle":0,"index":39,"text":"char(2) references Dept(D#) on delete cascade,","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"b5cb2e88-4570-43a6-a8bf-cce626ff8962","page_size":[595,841],"block_position":"20-30"},{"bbox":[97,593,155,602],"type":"text","angle":0,"index":40,"text":" Sclass char(6) );","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"361a23e4-7512-4e44-a3a8-2c4bd298f58a","page_size":[595,841],"block_position":"20-31"},{"bbox":[97,602,245,612],"type":"text","angle":0,"index":41,"text":"//假定Ssex只能取{男，女},1==0.0 and","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"feea1c9a-67c8-430b-a270-82abe6e414c8","page_size":[595,841],"block_position":"20-35"},{"bbox":[164,665,396,677],"type":"text","angle":0,"index":45,"text":"Credit<=5.0).T# char(3) references Teacher(T#) on delete","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"bf4b5c0d-bfc4-407f-af80-b93811c98b5c","page_size":[595,841],"block_position":"20-36"},{"bbox":[164,679,207,689],"type":"text","angle":0,"index":46,"text":"cascade);","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":20,"id":"3e52054a-bbcf-4ecb-b40b-8f577966e039","page_size":[595,841],"block_position":"20-37"}],[{"bbox":[98,83,450,101],"type":"text","angle":0,"index":0,"text":"》一种关系约束类型，对多列或元组的值进行约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":21,"id":"3632c086-bbe8-4273-9e7c-06edc3bb597b","page_size":[595,841],"block_position":"21-0"},{"bbox":[126,106,595,294],"index":1,"angle":0,"type":"code","text":"```txt\n[CONSTRAINT constraintname] //为约束命名，便于以后撤消 \n{UNIQUE (colname {, colname..}) //几列值组合在一起是唯一 \n|PRIMARY KEY (colname {, colname..}) //几列联合为主键 \n|CHECK (search_condition) //元组多列值共同满足条件 \n//条件中只能使用同一元组的前值 \n|FOREIGN KEY (colname {, colname..}) \nREFERENCES tablename [(colname {, colname..})][DELETE CASCADE]\n```","id":"41ef60d5-e848-42dc-8f7f-7e55fcad95fa","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":21,"page_size":[595,841],"block_position":"21-1"},{"bbox":[154,299,404,314],"type":"text","angle":0,"index":2,"text":"引用另一表tablename的若干列的值作为外键","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":21,"id":"caeb3bbc-431e-425f-b2e9-2fa74c9fcdc1","page_size":[595,841],"block_position":"21-2"},{"bbox":[154,317,595,359],"type":"text","angle":0,"index":3,"text":">table_constr表约束：是应用在关系上，即对关系的多列或行约束，列约束是其特例","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":21,"id":"626b5da4-6ee9-4a59-95e4-d232277fd532","page_size":[595,841],"block_position":"21-3"},{"bbox":[99,421,377,489],"index":4,"angle":0,"type":"code","text":"```sql\nCreate Table Student (S# char(8) not null unique, Sname char(10), Ssex char(2) constraint ctssex check (Ssex='男' or Ssex='女'), Sage integer check (Sage>1 and Sage<150), D# char(2) references Dept(D#) on delete cascade, Sclass char(6), primary key(S#));\n```","id":"4675875b-d403-4caf-a557-fd7e504460d0","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":21,"page_size":[595,841],"block_position":"21-4"},{"bbox":[117,493,379,562],"index":5,"angle":0,"type":"code","text":"```txt\nCreate Table Course ( C# char(3) , Cname char(12), Chours integer, Credit float(1) constraint ctcredit check (Credit >=0.0 and Credit<=5.0) , T# char(3) references Teacher(T#) on delete cascade, primary key(C#, constraint ctc check(Chours/Credit = 20));\n```","id":"d9b881f2-fcd1-4dd1-a270-99c111ea991c","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":21,"page_size":[595,841],"block_position":"21-5"},{"bbox":[152,564,244,573],"index":6,"angle":0,"type":"code","text":"```txt\n//假定严格约束20学时一个学分\n```","id":"c35a8d81-9533-47d9-9a41-e0605aca4061","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":21,"page_size":[595,841],"block_position":"21-6"}],[{"bbox":[149,74,345,94],"type":"title","angle":0,"index":0,"text":"# 4.1.4约米的修改","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":22,"id":"108babf5-12e2-431d-98ce-2ff4f69d8bdf","page_size":[595,841],"block_position":"22-0"},{"bbox":[97,111,517,137],"type":"text","angle":0,"index":1,"text":"■先给约束命名，然后进行增加或者删除。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"a26bd5d3-93a2-46dd-8b02-27eb755b418b","page_size":[595,841],"block_position":"22-1"},{"bbox":[96,143,564,204],"type":"text","angle":0,"index":2,"text":"★命名： Constraint<约束名><约束定义>Eg.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"13370d68-1a7d-45c8-a984-61cb8f365c48","page_size":[595,841],"block_position":"22-2"},{"bbox":[122,210,464,235],"type":"text","angle":0,"index":3,"text":" eno char(2) constraint pk_emp,","id":"d00fdc09-e371-46bb-85b9-5028cf4b35e6","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"page_size":[595,841],"block_position":"22-3"},{"bbox":[120,243,595,294],"type":"text","angle":0,"index":4,"text":"2. sex char(2) constraint chk_sex check (sex IN","id":"91ad33cf-ee35-4582-9c9c-5465a6bdae0d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"page_size":[595,841],"block_position":"22-4"},{"bbox":[121,301,595,353],"type":"text","angle":0,"index":5,"text":"3. Constraint chk_namesex check( $\\mathrm { s e x } = \\mathrm { \\tilde { F } } \\mathrm { \\tilde { \\Omega } }$ or nanot like‘Ms.%)","id":"1a1413c4-525b-47c4-a461-6043d268dc2c","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"page_size":[595,841],"block_position":"22-5"},{"bbox":[131,360,452,386],"type":"text","angle":0,"index":7,"text":"★增加：alter table ","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"7c62cb25-f8b4-4e49-adba-1d24c27b3a97","page_size":[595,841],"block_position":"22-6"},{"bbox":[230,391,595,417],"type":"text","angle":0,"index":8,"text":"Add Constraint<约束名><约束定义>","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"3aa2e577-7cb3-474e-9bef-e8c5451f55c6","page_size":[595,841],"block_position":"22-7"},{"bbox":[132,424,452,451],"type":"text","angle":0,"index":9,"text":"★删除：alter table ","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"40989429-215d-4f85-bbbb-8796cc898880","page_size":[595,841],"block_position":"22-8"},{"bbox":[303,457,552,483],"type":"text","angle":0,"index":10,"text":"drop Constraint <约束名>","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"11511bb2-c3f7-436f-8143-b055c43fb62f","page_size":[595,841],"block_position":"22-9"},{"bbox":[86,576,206,590],"type":"title","angle":0,"index":11,"text":"# 是拒绝、级联删除、置空","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":22,"id":"6ad7b039-e06f-40a3-a1e6-b4c58e30b2ef","page_size":[595,841],"block_position":"22-10"},{"bbox":[87,592,185,606],"type":"text","angle":0,"index":12,"text":"1. 属性（列）级约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"2d3dc317-8b67-41d0-b11f-f194375ed284","page_size":[595,841],"block_position":"22-11"},{"bbox":[104,608,171,620],"type":"text","angle":0,"index":13,"text":"NOT NULL","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"569100a1-021f-4923-8d7e-65af6f1cad07","page_size":[595,841],"block_position":"22-12"},{"bbox":[122,624,294,637],"type":"text","angle":0,"index":14,"text":"禁止该列出现 NULL 值（必须填写）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"b1b71f10-ce62-47c2-9e1c-8cf50e2596fc","page_size":[595,841],"block_position":"22-13"},{"bbox":[104,640,163,651],"type":"text","angle":0,"index":15,"text":". UNIQUE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"45a221ac-af5b-4c66-a22a-3e0b4345cadd","page_size":[595,841],"block_position":"22-14"},{"bbox":[122,655,504,684],"type":"text","angle":0,"index":16,"text":"确保该列的值唯一（允许 NULL，但多个NULL可能被视为不同值，取决于数据库实现）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"839ae0d3-1499-436f-9fc3-f8dcf57f2f76","page_size":[595,841],"block_position":"22-15"},{"bbox":[105,687,155,698],"type":"text","angle":0,"index":17,"text":"CHECK","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"1a86aee6-bec2-4d5d-8681-f5eaffa69500","page_size":[595,841],"block_position":"22-16"},{"bbox":[122,702,327,715],"type":"text","angle":0,"index":18,"text":"定义列值的检查条件，如 CHECK (age $\\bf { \\sigma } > 1 8$ )。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"9a1b65b3-c070-4689-b8f9-742d84fd8244","page_size":[595,841],"block_position":"22-17"},{"bbox":[105,718,164,729],"type":"text","angle":0,"index":19,"text":"DEFAULT","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"a44ab361-c510-4949-9752-df71189375b1","page_size":[595,841],"block_position":"22-18"},{"bbox":[122,733,292,746],"type":"text","angle":0,"index":20,"text":"设置默认值，如 DEFAULT 'unknown'。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":22,"id":"0c2ec16e-7305-4367-92f7-7f89bc7f58e8","page_size":[595,841],"block_position":"22-19"}],[{"bbox":[86,79,185,92],"type":"title","angle":0,"index":0,"text":"# 2. 表（外键）级约束","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"a8308a59-9b7d-4a6e-8ba0-9399cd31a3e6","page_size":[595,841],"block_position":"23-0"},{"bbox":[86,94,505,123],"type":"text","angle":0,"index":1,"text":"这些约束用于维护参照完整性（Referential Integrity），定义当父表（被引用表）的记录被更新或删除时，子表（引用表）如何处理相关记录：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"id":"eeffb30c-9ee5-4185-9fb0-0e0a9cf47f31","page_size":[595,841],"block_position":"23-1"},{"bbox":[86,132,512,388],"index":2,"angle":0,"type":"table_body","img_path":"/","id":"880bf352-9096-4c21-899d-a4bf7b6f2a44","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
约束操作说明
RESTRICT (拒绝)默认行为，阻止删除或修改父表记录（如果子表有引用）。
NO ACTION类似于 RESTRICT，但某些数据库（如 PostgreSQL）会在事务结束时检查。
CASCADE (级联)父表记录被删除或更新时，自动删除或更新子表对应的记录。
SET NULL (置空)父表记录被删除或更新时，子表的外键列设为 NULL（要求外键列允许NULL）。
SET DEFAULT父表记录被删除或更新时，子表的外键列设为默认值（需定义 DEFAULT T）。
","page_idx":23,"page_size":[595,841],"block_position":"23-2"},{"bbox":[87,406,154,418],"type":"title","angle":0,"index":3,"text":"#  Check 约束：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"7595d278-6357-4921-96aa-d7652031d40e","page_size":[595,841],"block_position":"23-3"},{"bbox":[88,421,295,433],"type":"text","angle":0,"index":4,"text":"$\\star$ 约束条件可以是任何 Where 中出现的字句；","id":"94d3c030-eab3-4957-912a-1039554c9694","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-4"},{"bbox":[88,437,201,449],"type":"text","angle":0,"index":5,"text":"故具有很强的表述能力；","id":"7865ef55-3620-4e5b-9e18-37b8793e2439","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-5"},{"bbox":[89,453,210,465],"type":"text","angle":0,"index":6,"text":"$\\star$ 常用于数据的值域约束；","id":"113c6c47-772c-41c1-9dfa-a72dea874002","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-6"},{"bbox":[88,469,294,481],"type":"title","angle":0,"index":8,"text":"# 三、User Defined Integrity and Default、Check","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"6c5d18a8-3e52-4315-ba3e-48688aa06b12","page_size":[595,841],"block_position":"23-7"},{"bbox":[88,484,103,496],"type":"title","angle":0,"index":9,"text":"# Eg.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"38777d17-e6ab-4af1-b2df-9e209d40b9b1","page_size":[595,841],"block_position":"23-8"},{"bbox":[88,498,333,512],"type":"text","angle":0,"index":10,"text":"1. sex char(2) check (sex IN (‘男’,‘女’)) default‘男 ’，","id":"88552431-8076-46a3-b5e0-3fa031dccaa0","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-9"},{"bbox":[88,515,267,528],"type":"text","angle":0,"index":11,"text":"2. age int check (age>=16 and age $\\mathtt { < } \\mathtt { = } 7 0$ )，","id":"d91a532a-ecc4-4db0-96fd-d92cfb3aa5e7","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-10"},{"bbox":[88,531,103,542],"type":"title","angle":0,"index":13,"text":"# Eg.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"25b4c136-ad2d-4b7b-ba81-e7cc83c4f13e","page_size":[595,841],"block_position":"23-11"},{"bbox":[88,545,333,560],"type":"text","angle":0,"index":14,"text":"1. sex char(2) check (sex IN (‘男’,‘女’)) default‘男 ’，","id":"c27f9cca-157b-4bc6-b6fa-7f6987179e2b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-12"},{"bbox":[88,562,267,575],"type":"text","angle":0,"index":15,"text":"2. age int check (age>=16 and age $\\mathtt { < } \\mathtt { = } 7 0$ )，","id":"ae08b318-5a26-4d1e-a907-e8bf1572a1c3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-13"},{"bbox":[88,592,154,606],"type":"title","angle":0,"index":17,"text":"# 触发器 Trigger","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"ef24ce1a-ed38-4457-9dd8-12ca6c1a1cdc","page_size":[595,841],"block_position":"23-14"},{"bbox":[87,608,411,652],"type":"text","angle":0,"index":18,"text":"Create Table中的表约束和列约束基本上都是静态的约束，也基本上都是对单一列或单一元组的约束(尽管有参照完整性)，为实现动态约束以及多个元组之间的完整性约束，就需要触发器技术 Trigger","id":"de7db5e0-18a5-4e7d-856c-98397c00f216","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-15"},{"bbox":[88,655,411,699],"type":"text","angle":0,"index":19,"text":"Trigger是一种过程完整性约束(相⽐之下，Create Table中定义的都是非过程性约束),是一段 SQL 程序，该程序在对表或视图执行 UPDATE、INSERT 或 DELETE 操作时自动触发执行。","id":"4ffc74a3-1414-4f64-8e3e-98df375a6202","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":23,"page_size":[595,841],"block_position":"23-16"},{"bbox":[88,702,141,714],"type":"title","angle":0,"index":21,"text":"# 基本语法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"6e12556b-90bb-4bf5-9071-3cdf0353f277","page_size":[595,841],"block_position":"23-17"},{"bbox":[88,718,161,729],"type":"title","angle":0,"index":22,"text":"# CREATETRIGGER","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"6c3989b2-5c53-4c58-8c06-b565cc91bdca","page_size":[595,841],"block_position":"23-18"},{"bbox":[88,733,149,745],"type":"title","angle":0,"index":23,"text":"# trigger_name","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"97c47c98-dc3a-4277-bc5d-bd3e37f85642","page_size":[595,841],"block_position":"23-19"},{"bbox":[88,749,161,760],"type":"title","angle":0,"index":24,"text":"# BEFORE | AFTER","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":23,"id":"fbf45360-cb12-4e78-9bfa-eccdf883d0a1","page_size":[595,841],"block_position":"23-20"}],[{"bbox":[86,79,385,122],"index":0,"angle":0,"type":"code","text":"```sql\n{ INSERT | DELETE | UPDATE [OF colname {, colname...}] } ON tablename [REFERENCING corr_name_def {, corr_name_def...}] [FOR EACH ROW | FOR EACH STATEMENT]\n```","id":"553870b4-d308-4be8-983b-214483a9f883","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-0"},{"bbox":[86,125,503,138],"type":"text","angle":0,"index":1,"text":"//对更新操作的每一条结果(前者:行级触发器)，或整个更新操作完成(后者：语句级触发器)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"b8b51ef7-958f-4311-a2b1-d1960be42710","page_size":[595,841],"block_position":"24-1"},{"bbox":[87,141,210,168],"index":2,"angle":0,"type":"code","text":"```objectivec\n[WHEN (search_condition)] { statement\n```","id":"3db52390-c99b-4892-8686-d464ff7b84a3","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-2"},{"bbox":[86,172,246,185],"type":"text","angle":0,"index":3,"text":"//检查条件，如满足执行下述程序","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"95268586-e244-4016-a3d4-e9137e4aab4e","page_size":[595,841],"block_position":"24-3"},{"bbox":[86,188,298,200],"type":"text","angle":0,"index":4,"text":"//单行程序直接书写，多行程序要用下行方式","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"d2ccab41-9a1c-41da-a8c4-3787409fa53b","page_size":[595,841],"block_position":"24-4"},{"bbox":[88,203,307,216],"index":5,"angle":0,"type":"code","text":"```typescript\nBEGIN ATOMIC statement; {statement;...} END }\n```","id":"c71cdabf-e3c3-4a52-9321-09c7225924d0","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-5"},{"bbox":[86,219,369,294],"index":6,"angle":0,"type":"code","text":"```txt\n> 触发器 Trigger 意义：当某一事件发生时(Before|After)，对该事件产生的结果(或是每一元组，或是整个操作的所有元组)，检查条件 search_condition，如果满足条件，则执行后面的程序段。条件或程序段中引用的变量可用 corr_name_def 来限定。\n```","id":"6d1d2284-67f3-48bf-a363-09a4ef604f9b","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-6"},{"bbox":[101,296,484,312],"type":"text","angle":0,"index":7,"text":"事件：BEFORE|AFTER{INSERT|DELETE| UPDATE..}","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"68894e16-ec92-4331-8010-eb41d663aca9","page_size":[595,841],"block_position":"24-7"},{"bbox":[101,316,562,332],"type":"text","angle":0,"index":8,"text":"□当一个事件(Insert,Delete,或Update)发生之前Before或发生之后After触发","id":"a6863b2d-caa8-40e7-b58d-c4bcd5d167f6","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-8"},{"bbox":[101,336,570,368],"type":"text","angle":0,"index":9,"text":"□DELETE/INSERT/UPDATE操作发生，执行触发器操作需处理两组值：更新前的值和更新后的值，这两个值由corr_name_def的使用来区分","id":"080edd2e-a9b0-486c-9e77-db0a4f9aff10","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-9"},{"bbox":[101,373,571,421],"type":"text","angle":0,"index":10,"text":"□对于UPDATE触发器，每当UPDATE语句修改由OF子句指定的列值时，激发触发器；如果忽略OF子句，每当UDPATE语句修改表的任何列值时，DBMS都将激发触发器。","id":"42880a1f-0796-4ff4-bdd5-31914ae41ef9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-10"},{"bbox":[94,431,381,531],"index":12,"angle":0,"type":"code","text":"```sql\nCREATE TRIGGER trigger_name BEFORE|AFTER \n{INSERT|DELETE|UPDATE [OF colname{,colname...}]} \nON tablename [REFERENCING corr_name_def{,corr_name_def...}] \n[FOR EACH ROW|FOR EACH STATEMENT] \n//对更新操作的每一条结果(前者)，或整个更新操作完成(后者) \n[WHEN (search_condition)] //检查条件，如满足执行下述程序 \n{statement //单行程序直接书写，多行程序要用下行方式 \n|BEGIN ATOMIC statement; {statement,...} END}\n```","id":"cf7faeb7-c51f-42c6-8be5-3bd7ddedd626","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":24,"page_size":[595,841],"block_position":"24-11"},{"bbox":[402,437,571,515],"index":13,"angle":0,"type":"image","img_path":"/97868f142be5baa0f0e5950e2a9471a66963130572466d4d12982117187ddefe.jpg","color":{"line":"rgba(89, 92, 220, 1)","fill":"rgba(89, 92, 220, 1)"},"img_ratio":0.28403361344537814,"page_idx":24,"id":"7d38ed9c-2e5f-4adb-829d-b73a11afe210","page_size":[595,841],"block_position":"24-12"},{"bbox":[86,561,229,574],"type":"text","angle":0,"index":14,"text":"属性上的约束条件：NOT NULL","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"985c71b7-2107-453f-b1ee-a702571c108c","page_size":[595,841],"block_position":"24-13"},{"bbox":[87,577,126,589],"type":"text","angle":0,"index":15,"text":"UNIQUE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"e4c427fa-c35e-44fd-bff3-f981e3fea9fd","page_size":[595,841],"block_position":"24-14"},{"bbox":[87,593,119,603],"type":"text","angle":0,"index":16,"text":"CHECK","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"c4256434-ef9c-4bd1-aaea-19971d7eae4b","page_size":[595,841],"block_position":"24-15"},{"bbox":[87,608,306,621],"type":"text","angle":0,"index":17,"text":"表上的约束条件 CASCADDE NO ACTION RESTRICT","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"a41e3773-d3ee-47af-9464-ae7d47e9c5bf","page_size":[595,841],"block_position":"24-16"},{"bbox":[86,640,138,652],"type":"title","angle":0,"index":18,"text":"# 2.1 安全性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":24,"id":"d691d5eb-d65c-4572-9674-ccb9f7687753","page_size":[595,841],"block_position":"24-17"},{"bbox":[86,655,227,667],"type":"text","angle":0,"index":19,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"fc60f3cb-1b40-4803-b7be-e8bd801b1d9a","page_size":[595,841],"block_position":"24-18"},{"bbox":[87,671,185,683],"type":"text","angle":0,"index":20,"text":"知识点：安全性定义","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"a2aeac05-b000-480b-9909-248b459911be","page_size":[595,841],"block_position":"24-19"},{"bbox":[86,702,346,714],"type":"text","angle":0,"index":21,"text":"数据库的完整性是指尽可能避免对数据库的无意的滥用；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"bbdc5ae7-b253-49e7-85aa-d1f001cfcdd1","page_size":[595,841],"block_position":"24-20"},{"bbox":[86,718,346,730],"type":"text","angle":0,"index":22,"text":"数据库的安全性是指尽可能避免对数据库的恶意的滥用。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"ffa23015-adf0-49d3-ab1e-7e987fe61da4","page_size":[595,841],"block_position":"24-21"},{"bbox":[86,749,430,761],"type":"text","angle":0,"index":23,"text":"数据库系统的安全措施是建立在计算机系统基础之上的，通常有五个方面。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":24,"id":"c210cf90-e5c9-444c-a430-fff54db1d78b","page_size":[595,841],"block_position":"24-22"}],[{"bbox":[94,79,192,91],"type":"text","angle":0,"index":0,"text":"（1） 用户标识和鉴定","id":"3807e173-fcd2-42ef-8028-5386cddc9dba","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-0"},{"bbox":[95,95,160,106],"type":"text","angle":0,"index":1,"text":"（2） 存取控制","id":"2c6f492c-0100-4d13-8841-eb05946beb9b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-1"},{"bbox":[95,111,160,122],"type":"text","angle":0,"index":2,"text":"（3） 定义视图","id":"803d3efa-9e1c-4171-886e-930610e36dde","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-2"},{"bbox":[95,126,139,137],"type":"text","angle":0,"index":3,"text":"（4） 审计","id":"43f701d6-7e3b-4c0e-94a5-b36555f324a4","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-3"},{"bbox":[94,142,160,153],"type":"text","angle":0,"index":4,"text":"（5） 数据加密","id":"b22ae0ec-3638-442e-aae5-49ce15deb711","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-4"},{"bbox":[87,157,293,169],"type":"text","angle":0,"index":6,"text":"用户或应用程序使用数据库的方式称为权限。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"52d0afab-ea35-48e2-a8bb-d411580b77f1","page_size":[595,841],"block_position":"25-5"},{"bbox":[86,188,503,216],"type":"text","angle":0,"index":7,"text":"授权子系统可以保证用户只能进行其权限范围内的操作，并允许有特定权限的用户有选择地和动态地把这些权限授予其他用户。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"45f91355-4d4f-4b45-b25b-bb3a70bb5d32","page_size":[595,841],"block_position":"25-6"},{"bbox":[95,220,158,232],"type":"text","angle":0,"index":8,"text":"（1）用户权限","id":"9762208b-628a-49af-a1bd-b0fc7563016b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-7"},{"bbox":[95,235,158,247],"type":"text","angle":0,"index":9,"text":"（2）授权语句","id":"2869403d-0593-4478-a62b-a760004b85f6","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"page_size":[595,841],"block_position":"25-8"},{"bbox":[94,250,413,263],"type":"text","angle":0,"index":11,"text":"GRANT <权限表> ON <数据库对象> TO <用户名> [WITH GRANT OPTION]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"16f2b8c1-47ad-444d-a62d-df8e67a9158a","page_size":[595,841],"block_position":"25-9"},{"bbox":[95,266,158,279],"type":"text","angle":0,"index":12,"text":"（3）回收权限","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"62179f00-8323-4c19-b0e6-ee0502a49e99","page_size":[595,841],"block_position":"25-10"},{"bbox":[86,281,372,294],"type":"text","angle":0,"index":13,"text":"REVOKE <权限表> ON <数据库对象> FROM <用户名 $>$ [CASCADE]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"b2a550cf-a9c8-4083-95c9-592a573b8c77","page_size":[595,841],"block_position":"25-11"},{"bbox":[86,296,426,310],"type":"text","angle":0,"index":14,"text":"用户与角色：它们之间的关系、权限的继承性、角色授权的高效和便捷性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"3e7cb290-d7b5-489e-a594-94062276661b","page_size":[595,841],"block_position":"25-12"},{"bbox":[86,312,503,341],"type":"text","angle":0,"index":15,"text":"会判断用户加入某个角色后的最终的权限是什么（自己被授予的权限加上继承了角色的权限，但要去掉被DENY掉的权限）（详见第四章安全性补充PPT）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"e5d3add2-436c-4d4e-befc-eb6f9691345b","page_size":[595,841],"block_position":"25-13"},{"bbox":[86,343,503,372],"type":"text","angle":0,"index":16,"text":"视图是从一个或几个基本表导出的表，是虚表，视图定义后可以像基本表一样用于查询和删除， 但其更新操作(增、删、改)会受到限制。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"d515acfa-5e8b-4d86-8b7d-e6601b7fd193","page_size":[595,841],"block_position":"25-14"},{"bbox":[86,390,505,418],"type":"text","angle":0,"index":17,"text":"视图机制把用户可以使用的数据定义在视图中，这样用户就不能使用视图定义外的其他数据，从而保证了数据库的安全性。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"2a6d0e05-5046-4728-8c4d-ccf4577dbaf3","page_size":[595,841],"block_position":"25-15"},{"bbox":[86,422,419,434],"type":"text","angle":0,"index":18,"text":"视图机制使系统具有三个优点：数据安全性、数据独立性和操作简便性。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"270ff10d-4ed7-40ae-8f89-eb6446036f86","page_size":[595,841],"block_position":"25-16"},{"bbox":[86,453,503,465],"type":"text","angle":0,"index":19,"text":"事务是一个操作序列。 这些操作要么什么都做，要么都不做，是一个不可分割的工作单位","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"55603e8c-6d14-400f-b9e0-8bad170e0364","page_size":[595,841],"block_position":"25-17"},{"bbox":[86,484,505,528],"type":"text","angle":0,"index":20,"text":"在应用程序 中 ，事务以 BEGIN TRANSACTION 语 句 开 始 ， 以 COMMIT(提交)语 句 或ROLLBACK(回退或撤消)语句结束。 一个程序的执行可通过若干事务的执行序列来完成。事务是不能嵌套的，可恢复的操作必须在一个事务的界限内才能执行.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":25,"id":"31913370-54ce-4f3e-8119-99af66899c99","page_size":[595,841],"block_position":"25-18"}],[{"bbox":[131,127,186,157],"type":"title","angle":0,"index":0,"text":"# 例1：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":26,"id":"66d69a13-0539-4fa2-8ac3-4f15e40e5a32","page_size":[595,841],"block_position":"26-0"},{"bbox":[129,164,558,232],"type":"text","angle":0,"index":1,"text":" grant select on Student to public例2：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"ee11d31e-f6ea-489f-96dd-fece770c9d6e","page_size":[595,841],"block_position":"26-1"},{"bbox":[145,239,485,270],"type":"text","angle":0,"index":2,"text":" grant all on Student to u2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"cbe5d83c-2095-467c-ba57-22328e550329","page_size":[595,841],"block_position":"26-2"},{"bbox":[131,275,186,304],"type":"title","angle":0,"index":3,"text":"# 例3:","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":26,"id":"a6c19372-ab22-4c7c-980a-8d61808e6f00","page_size":[595,841],"block_position":"26-3"},{"bbox":[134,313,593,378],"type":"text","angle":0,"index":4,"text":"grant update(Sno),select on Student例4:","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"c5583980-b123-4e48-9fa6-f5eaf75ac410","page_size":[595,841],"block_position":"26-4"},{"bbox":[136,387,437,420],"type":"text","angle":0,"index":5,"text":" grant insert on SC to u5","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"d0b8fc3d-198f-4dd2-b3bf-f20bb0c53582","page_size":[595,841],"block_position":"26-5"},{"bbox":[176,425,386,456],"type":"text","angle":0,"index":6,"text":"with grant option","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"beba6311-2bce-441d-b209-6afc42e1792f","page_size":[595,841],"block_position":"26-6"},{"bbox":[87,468,160,481],"type":"title","angle":0,"index":7,"text":"# 3.2 事务的性质","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":26,"id":"69d355f8-3b71-4bdc-9ea8-7ec8982206b9","page_size":[595,841],"block_position":"26-7"},{"bbox":[86,499,172,512],"type":"text","angle":0,"index":8,"text":"事务的ACID性质：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"880ad472-c93d-4b2d-8506-83aba7c3b225","page_size":[595,841],"block_position":"26-8"},{"bbox":[86,515,442,529],"type":"text","angle":0,"index":9,"text":"原子性(atomicity)、一致性(consistency)、隔离性(isolation)和持久性(durability)。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"id":"e29a7070-a88a-487c-b1eb-d673c3842d0d","page_size":[595,841],"block_position":"26-9"},{"bbox":[87,546,201,559],"index":10,"angle":0,"type":"table_caption","text":"3.3 故障类型和恢复方法","id":"c1a0dfdc-ca84-4447-9616-640d01bafbeb","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":26,"page_size":[595,841],"block_position":"26-10"},{"bbox":[94,560,508,721],"index":11,"angle":0,"type":"table_body","img_path":"/","id":"2711e71c-8efb-4d97-b433-ad9d85575239","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
事务故障非预期的事务故障，以由事务程序自动处理
系统故障在硬件故障、软件错误的影响下，虽引起内存信息丢失，但未破坏外存中的数据。重新启动时,恢复子系统将所有非正常终止的事务回退,恢复到正确状态。
介质故障\n计算机病毒等需要DBA的介入，\n通过DBMS把其他务份磁盘或第三级介质中的内容再复制回来
","page_idx":26,"page_size":[595,841],"block_position":"26-11"}],[{"bbox":[88,95,232,107],"type":"title","angle":0,"index":0,"text":"# 3.4 恢复的基本原则和实现方法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":27,"id":"7fb0cf75-a15a-4ede-b924-5a40dc2db427","page_size":[595,841],"block_position":"27-0"},{"bbox":[86,125,367,138],"type":"text","angle":0,"index":1,"text":"恢复的基本原则很简单，就是“冗余”，即数据的重复存储。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"be853016-bbc3-44c0-a8fc-fd09afc5f4bd","page_size":[595,841],"block_position":"27-1"},{"bbox":[87,142,146,153],"type":"text","angle":0,"index":2,"text":"实现方法有：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"1f3e0c55-482b-4878-956a-4c966b717a5a","page_size":[595,841],"block_position":"27-2"},{"bbox":[87,157,273,169],"type":"text","angle":0,"index":3,"text":"(1)定期对数据库进行复制或转储(dump)。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"7a529aef-4a93-4fc4-ac79-d3ea2f69fb1f","page_size":[595,841],"block_position":"27-3"},{"bbox":[86,173,376,185],"type":"text","angle":0,"index":4,"text":"Notice:几个概念：静态转储、动态转储、海量转储和增量转储。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"49d02988-09c3-4c32-b643-fcf8e3bdece4","page_size":[595,841],"block_position":"27-4"},{"bbox":[104,188,424,200],"type":"text","angle":0,"index":5,"text":"静态存储是指转储期间不允许对数据库进行任何存取、修改活动；","id":"1475275f-6051-403e-9cd7-3ed7f337cb59","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-5"},{"bbox":[104,203,503,232],"type":"text","angle":0,"index":6,"text":"动态存储是指转储期间允许对数据库进行存取、修改；即转储和用户事务可以并发执行；","id":"eb1475c8-7f18-4b01-b0ac-519084c5f9a1","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-6"},{"bbox":[104,235,287,247],"type":"text","angle":0,"index":7,"text":"海量存储是指每次转储全部数据库；","id":"bc4ee50a-2423-4658-bdbc-98a5e2414644","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-7"},{"bbox":[104,250,360,263],"type":"text","angle":0,"index":8,"text":"增量存储则指每次只转储上次转储后更新过的数据。","id":"c4a05765-84c2-43d8-baf4-0b7bab8be3e4","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-8"},{"bbox":[87,266,190,279],"type":"text","angle":0,"index":10,"text":"(2)建立“日志”文件。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"e8e116d4-1de1-49b9-a734-101c3688c0c4","page_size":[595,841],"block_position":"27-9"},{"bbox":[86,281,504,325],"type":"text","angle":0,"index":11,"text":"(3)恢复。发生故障时有两种处理方法，如数据库已破坏， 则由 DBA装入最近备份的数据库然后利用\"日志文件\"执行REDO(重做)操作。如数据库未被损坏， 但某些数据不可靠，则系统会自动执行UNDO操作恢复数据。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"abb841e2-89d6-4d9f-b309-e758cda6450a","page_size":[595,841],"block_position":"27-10"},{"bbox":[87,328,251,341],"type":"text","angle":0,"index":12,"text":"注意每种故障策略的不同恢复手段。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"86dbbfa3-d513-4488-868c-8f64793e6b26","page_size":[595,841],"block_position":"27-11"},{"bbox":[87,343,205,356],"type":"text","angle":0,"index":13,"text":"并发控制带来的三类问题","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"6a59d24e-b546-4752-b9cb-30f10473b90b","page_size":[595,841],"block_position":"27-12"},{"bbox":[92,359,148,372],"type":"text","angle":0,"index":14,"text":"(1)丢失更新","id":"2fc6af19-00c8-48ec-8132-8a3ebcf27228","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-13"},{"bbox":[92,375,159,387],"type":"text","angle":0,"index":15,"text":"(2)不可重复读","id":"cfb36a6c-9ee0-4463-9126-16b5a3830773","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-14"},{"bbox":[92,390,470,418],"type":"text","angle":0,"index":16,"text":"(3)读“脏数据”(在数据库技术中，未提交的随后又被撤消的数据为“脏数据”。)以上三类问题要做到理解。","id":"c07475df-132f-4a85-9516-4276272bd4de","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"page_size":[595,841],"block_position":"27-15"},{"bbox":[86,437,504,466],"type":"text","angle":0,"index":18,"text":"解决并发控制带来的问题，通常要采用封锁(locking)技术，常用的封锁有：排它型封锁(X封锁)和共享型封锁(S封锁)两种。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"bf1c2f3b-8fb5-418c-94fd-469490faad61","page_size":[595,841],"block_position":"27-16"},{"bbox":[87,484,127,496],"type":"title","angle":0,"index":19,"text":"# 4.2 封锁","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":27,"id":"f4ae2e51-aa37-4c73-87cc-f75875232292","page_size":[595,841],"block_position":"27-17"},{"bbox":[87,499,227,512],"type":"text","angle":0,"index":20,"text":"考核要求：达到“领会”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"98c1f165-6219-4ae9-a074-852e4705e1a1","page_size":[595,841],"block_position":"27-18"},{"bbox":[86,515,411,529],"type":"text","angle":0,"index":21,"text":"知识点：排它锁（X LOCK），共享锁（S LOCK），并发事务的可串行化","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"10d31b02-fa14-4868-8d55-25756ca11f3b","page_size":[595,841],"block_position":"27-19"},{"bbox":[86,546,508,576],"type":"text","angle":0,"index":22,"text":"封锁就是事务T可以向系统发出请求，对某个数据对象（通常是记录）加锁。 于是事务 T对这个数据对象就有一定的控制，其他事务不能更新此数据直到 T释放(Unlock)它的锁为止。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"33ee3421-1f59-46c9-a4b5-8660f7aa0bcf","page_size":[595,841],"block_position":"27-20"},{"bbox":[86,608,504,638],"type":"text","angle":0,"index":23,"text":"X封锁：如果事务T对数据R实现X封锁，那么其他的事务要等T解除X封锁以后，才能对这个数据进行封锁。 只有获准X封锁的事务，才能对被封锁的数据进行修改。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"c7471492-0a54-4bd4-9cce-55e46d9c8547","page_size":[595,841],"block_position":"27-21"},{"bbox":[86,655,504,700],"type":"text","angle":0,"index":24,"text":"S封锁--如果事务T对某数据R加上S封锁，那么其它事务对数据R的X封锁便不能成功，而对数据R的S封锁请求可以成功。 这就保证了其他事务可以读取 R但不能修改R，直到事务T释放S封锁。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"2366a3a2-556b-4510-9688-badcf182a137","page_size":[595,841],"block_position":"27-22"},{"bbox":[86,717,504,746],"type":"text","angle":0,"index":25,"text":"事务的执行次序称为“调度”。如果多个事务依次执行，则称为事务的串行调度。 如果利用分时的方法，同时处理多个事务，则称为事务的并发调度。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"b75f9325-698b-4504-9440-ee92d7bed6c4","page_size":[595,841],"block_position":"27-23"},{"bbox":[91,749,504,762],"type":"text","angle":0,"index":26,"text":"可串行化调度：如果一个并发调度的结果与某一串行调度执行结果等价，那么这个并发调","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":27,"id":"fc583e70-02e7-4980-92da-7ff4ecb403a8","page_size":[595,841],"block_position":"27-24"}],[{"bbox":[87,79,199,92],"type":"text","angle":0,"index":0,"text":"度称为是可串化的调度。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"96ee0570-81fd-49ad-8200-f1a41948855c","page_size":[595,841],"block_position":"28-0"},{"bbox":[86,110,160,122],"type":"title","angle":0,"index":1,"text":"# 4.3 活锁和死锁","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":28,"id":"c15a950b-d38c-4a6a-91f6-254e18f4d1eb","page_size":[595,841],"block_position":"28-1"},{"bbox":[86,125,227,138],"type":"text","angle":0,"index":2,"text":"考核要求：达到“领会”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"479ec125-be1a-46cd-890c-146590e27936","page_size":[595,841],"block_position":"28-2"},{"bbox":[86,141,301,155],"type":"text","angle":0,"index":3,"text":"知识点：活锁及其避免方法；死锁及消除方法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"2d5d9509-54a9-48aa-a024-23d914628e27","page_size":[595,841],"block_position":"28-3"},{"bbox":[86,172,367,185],"type":"text","angle":0,"index":4,"text":"活锁：是指某个事务永远处于等待状态，得不到执行的现象。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"dc0be95d-bc5a-4468-81a1-148760d53880","page_size":[595,841],"block_position":"28-4"},{"bbox":[93,188,301,201],"type":"text","angle":0,"index":5,"text":"避免活锁的方法是采用“先来先服务”策略。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"bbd33afc-57c3-4c48-8f10-bbaf4de9d830","page_size":[595,841],"block_position":"28-5"},{"bbox":[86,203,503,216],"type":"text","angle":0,"index":6,"text":"死锁：有两个或以上的事务处于等待状态，每个事务都在等待另一个事务解除封锁， 它才","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"88fd01f6-a351-4aa9-bf80-b20289b37ad0","page_size":[595,841],"block_position":"28-6"},{"bbox":[86,219,409,232],"type":"text","angle":0,"index":7,"text":"能继续执行下去，结果任何一个事务都无法执行，这种现象就是死锁。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"2b52b35a-90d1-4cf8-858e-20ce17e4d154","page_size":[595,841],"block_position":"28-7"},{"bbox":[86,234,498,264],"type":"text","angle":0,"index":8,"text":"解除死锁的方法是由DBMS中的“死锁测试程序”来检查，如发现死锁则牺牲一个事务，并做回退操作,解除它的所有封锁。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"9a01970f-e5f6-4fda-8346-bfa7504f26f8","page_size":[595,841],"block_position":"28-8"},{"bbox":[86,281,159,295],"type":"title","angle":0,"index":9,"text":"# 4.4 两段封锁法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":28,"id":"1120958c-dfdd-43d9-a213-03963c980349","page_size":[595,841],"block_position":"28-9"},{"bbox":[86,296,227,310],"type":"text","angle":0,"index":10,"text":"考核要求：达到“识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"0eb8a36f-0799-4775-a981-3a75dd317a68","page_size":[595,841],"block_position":"28-10"},{"bbox":[86,312,185,327],"type":"text","angle":0,"index":11,"text":"知识点：两段封锁法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"0dcd5e4a-8367-4ea7-af90-14a543713981","page_size":[595,841],"block_position":"28-11"},{"bbox":[86,343,305,356],"type":"text","angle":0,"index":12,"text":"两段封锁协议规定所有事务都要遵守下列规则：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"5948503d-90df-480d-942f-ec0af666557c","page_size":[595,841],"block_position":"28-12"},{"bbox":[91,359,415,373],"type":"text","angle":0,"index":13,"text":"(1)在对任何数据进行读写操作之前，事务首先要获得对该数据的封锁；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"626d4ef8-e559-4849-9312-7533717c29a5","page_size":[595,841],"block_position":"28-13"},{"bbox":[92,375,342,388],"type":"text","angle":0,"index":14,"text":"(2)在释放一个封锁之后，事务不再获得任何其他封锁。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"11cbc6bf-66b1-4194-a16f-446906c0e798","page_size":[595,841],"block_position":"28-14"},{"bbox":[86,406,405,435],"type":"text","angle":0,"index":15,"text":"事务：扩展阶段——可以申请封锁，但是不能解除任何已取得的封锁收缩阶段——可以释放封锁，但不能申请新的封锁","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":28,"id":"867b839c-6469-42b1-a92a-b5818cf66d03","page_size":[595,841],"block_position":"28-15"}],[{"bbox":[88,80,164,103],"type":"title","angle":0,"index":0,"text":"# 1.触发器","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":29,"id":"1fc84013-79ee-4b7a-b427-88215eb8a47c","page_size":[595,841],"block_position":"29-0"},{"bbox":[88,108,257,122],"type":"text","angle":0,"index":1,"text":"1.1触发器的概念、作用、使用场景","id":"a861aca9-3564-4a0e-a076-4f8c84169b3a","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-1"},{"bbox":[88,124,201,137],"type":"text","angle":0,"index":2,"text":"1.2创建触发器的语法：","id":"a8b11a0e-e87b-45b3-8654-7e023f0f8790","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-2"},{"bbox":[107,140,227,153],"type":"text","angle":0,"index":4,"text":"Create trigger触发器名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"d1fcb66a-695d-49c3-8c92-8449359e164e","page_size":[595,841],"block_position":"29-3"},{"bbox":[107,156,271,183],"index":5,"angle":0,"type":"code","text":"```txt\nOn/After insert |update|Delete AS\n```","id":"44853e2b-2977-4f06-b41e-56d95cacbf4d","color":{"line":"rgba(200, 140, 58, 1)","fill":"rgba(200, 140, 58, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-4"},{"bbox":[129,186,250,200],"type":"text","angle":0,"index":6,"text":"需要触发完成的 SQL语句","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"2552e7fd-cdf5-4164-b5e0-e0410fcbcf60","page_size":[595,841],"block_position":"29-5"},{"bbox":[88,217,200,231],"type":"text","angle":0,"index":7,"text":"1.3触发器中使用游标：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"0b1e2b6b-a63c-4bd9-b7c9-d95966c72588","page_size":[595,841],"block_position":"29-6"},{"bbox":[106,233,189,247],"type":"text","angle":0,"index":8,"text":"游标使用五部曲：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"c1f6ccd6-7ef6-4987-bb1f-23f620a79fdc","page_size":[595,841],"block_position":"29-7"},{"bbox":[113,248,177,262],"type":"text","angle":0,"index":9,"text":"（1）说明游标","id":"1902aff5-c360-4924-af46-644766ac486c","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-8"},{"bbox":[113,264,177,278],"type":"text","angle":0,"index":10,"text":"(2）打开游标","id":"bb9be810-748e-41a5-965a-d8cf1d5dc327","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-9"},{"bbox":[112,280,261,294],"type":"text","angle":0,"index":11,"text":"(3）推进游标指针并取当前记录","id":"6a6f2ec8-4962-48b9-a182-a41cf2619402","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-10"},{"bbox":[113,296,177,309],"type":"text","angle":0,"index":12,"text":"（4）关闭游标","id":"68d6e5bc-af11-44e6-abea-8905a44bd464","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-11"},{"bbox":[112,311,230,325],"type":"text","angle":0,"index":13,"text":"(5）释放游标占用的资源","id":"da866bc3-9215-4e62-a884-7376841356c6","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-12"},{"bbox":[87,327,355,341],"type":"text","angle":0,"index":15,"text":"DECLARE @no char(7), @ name char(10), @age tinyint","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"046b847a-96a8-43b3-a2c9-c9cc4603f3e1","page_size":[595,841],"block_position":"29-13"},{"bbox":[88,343,348,356],"type":"text","angle":0,"index":16,"text":"DECLARE SX CURSORFOR SELECT Sno,Sname, Sage","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"cac7bfbf-ade7-461c-bc0a-fdfb0aa4d7de","page_size":[595,841],"block_position":"29-14"},{"bbox":[139,358,213,370],"type":"text","angle":0,"index":17,"text":"FROM Student","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"b42bfb14-2ed7-49d4-ae52-905ad76c06e9","page_size":[595,841],"block_position":"29-15"},{"bbox":[298,358,371,371],"type":"text","angle":0,"index":18,"text":"/*说明游标*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"dbf7b946-f1d9-448f-b248-3f7280f14f1a","page_size":[595,841],"block_position":"29-16"},{"bbox":[88,374,139,386],"type":"text","angle":0,"index":19,"text":"OPEN SX ;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"16a67252-86e0-45f6-b069-598397dfbcf4","page_size":[595,841],"block_position":"29-17"},{"bbox":[309,374,382,386],"type":"text","angle":0,"index":20,"text":"/*打开游标*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"468ab901-63e7-496d-baf1-d67e855c279b","page_size":[595,841],"block_position":"29-18"},{"bbox":[88,390,271,402],"type":"text","angle":0,"index":21,"text":"FETCH SX INTO @no,@name,@ age ;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"f5b5d143-0022-468f-9435-f0705673c929","page_size":[595,841],"block_position":"29-19"},{"bbox":[146,404,453,417],"type":"text","angle":0,"index":22,"text":"游/*进游标指针推进一行，然后从结果集中取当前行，送相应主量","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"32d903f4-4b7d-44ec-a261-5012a0101040","page_size":[595,841],"block_position":"29-20"},{"bbox":[87,420,506,433],"type":"text","angle":0,"index":23,"text":"WHILE @ @ fetch_status=0 $\\prime ^ { \\star }$ 如果取到数据，用循环结构逐条处理结果集中的记录*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"bb5235c0-0d3a-45d1-9e90-09e82ab689d3","page_size":[595,841],"block_position":"29-21"},{"bbox":[88,436,120,448],"type":"text","angle":0,"index":24,"text":"BEGIN","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"626381b1-76d8-453e-bff3-07b83e49936c","page_size":[595,841],"block_position":"29-22"},{"bbox":[297,436,489,449],"type":"text","angle":0,"index":25,"text":"$\\prime ^ { \\star }$ 若出现 SQL语句错误，则退出循环*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"adf56f42-7350-410b-85b8-afc89e4548ff","page_size":[595,841],"block_position":"29-23"},{"bbox":[268,451,457,465],"type":"text","angle":0,"index":26,"text":"/*可以根据三个变量的值做相应的处理*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"4a25cd51-bcdd-4b3a-91fb-f2b6a291398b","page_size":[595,841],"block_position":"29-24"},{"bbox":[108,468,293,481],"type":"text","angle":0,"index":27,"text":"FETCH SX INTO @no,@ name,@ age ;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"3c60e1e2-cb28-4f51-ac72-fc5e266693c9","page_size":[595,841],"block_position":"29-25"},{"bbox":[146,482,461,496],"type":"text","angle":0,"index":28,"text":"/*游/*标指针向前推进一行，然后从结果集中取当前行，送相应主量","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"a032f798-4b77-4f61-8198-fb1fc0b674eb","page_size":[595,841],"block_position":"29-26"},{"bbox":[88,499,98,510],"type":"text","angle":0,"index":29,"text":"*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"399f8018-e29b-48c5-a848-40acac108f45","page_size":[595,841],"block_position":"29-27"},{"bbox":[88,515,111,525],"type":"text","angle":0,"index":30,"text":"END","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"02f1a7b4-7865-4532-822e-38673678a5bc","page_size":[595,841],"block_position":"29-28"},{"bbox":[88,530,139,542],"type":"text","angle":0,"index":31,"text":"CLOSE SX;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"67bd31f7-4412-4dd2-a476-e71799faab16","page_size":[595,841],"block_position":"29-29"},{"bbox":[204,529,277,542],"type":"text","angle":0,"index":32,"text":"/*关闭游标*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"fb6313a6-ccfb-4b36-b258-fcdefcdd0054","page_size":[595,841],"block_position":"29-30"},{"bbox":[88,545,171,558],"type":"text","angle":0,"index":33,"text":"DEALLOCATE SX;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"ffaf2b74-d28b-4aaf-9036-6f74db91970a","page_size":[595,841],"block_position":"29-31"},{"bbox":[200,545,351,558],"type":"text","angle":0,"index":34,"text":"$\\prime ^ { \\star }$ 释放游标所占用的系统资源*/","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"99011a38-61f3-4387-8f00-f3913b93a2c0","page_size":[595,841],"block_position":"29-32"},{"bbox":[88,576,480,590],"type":"text","angle":0,"index":35,"text":"1.4触发器的调用 (触发器无需用户调用，是在对表进行数据增删改时自动触发的)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"572dd391-e344-4204-afda-a4c94cb07f12","page_size":[595,841],"block_position":"29-33"},{"bbox":[87,610,180,631],"type":"title","angle":0,"index":36,"text":"# 2.存储过程","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":29,"id":"8ee724bb-7406-4ce7-838c-eaf77dcb1754","page_size":[595,841],"block_position":"29-34"},{"bbox":[87,638,266,651],"type":"text","angle":0,"index":37,"text":"2.1存储过程的概念、作用、使用场景","id":"7902e856-7316-40e3-8f14-87a94d670210","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-35"},{"bbox":[87,654,210,667],"type":"text","angle":0,"index":38,"text":"2.2创建存储过程的语法：","id":"02870a71-ca7c-4f49-9234-5a72b71a33d2","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-36"},{"bbox":[87,670,182,682],"type":"text","angle":0,"index":39,"text":"2.3 存储过程的调用","id":"224ca55c-c3f3-4101-a58e-622bc500ecbd","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"page_size":[595,841],"block_position":"29-37"},{"bbox":[88,685,220,698],"type":"text","angle":0,"index":41,"text":"详见教材P1235.5存储过程","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"c5f82302-36ef-4c31-9346-9fed844f28b5","page_size":[595,841],"block_position":"29-38"},{"bbox":[89,702,164,714],"type":"text","angle":0,"index":42,"text":"2 关系代数运算","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"6cd6ac25-36d2-4ecb-b4b8-93420a69bb6e","page_size":[595,841],"block_position":"29-39"},{"bbox":[87,718,221,730],"type":"text","angle":0,"index":43,"text":"2.1 关系代数的五个基本操作","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"69dc97b4-5458-4ac6-86ee-628ea71f26e6","page_size":[595,841],"block_position":"29-40"},{"bbox":[87,733,248,746],"type":"text","angle":0,"index":44,"text":"考核要求：达到“简单应用”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"f0c2cbb7-b59d-4657-8eb5-38d4213bc712","page_size":[595,841],"block_position":"29-41"},{"bbox":[87,749,278,761],"type":"text","angle":0,"index":45,"text":"知识点：五个基本操作的含义和运算应用","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":29,"id":"6d982f07-5324-4df8-ad64-3822e23457e3","page_size":[595,841],"block_position":"29-42"}],[{"bbox":[86,94,489,122],"type":"text","angle":0,"index":0,"text":"(1)并(∪)：两个关系需有相同的关系模式，并的对象是元组，由两个关系所有元组构成。RUS≡{t| t∈R ∨t∈S}","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"7dbfd903-fbd6-4272-b03f-860044ba8a72","page_size":[595,841],"block_position":"30-0"},{"bbox":[86,125,504,153],"type":"text","angle":0,"index":1,"text":"(2) 差(-)：同样，两个关系有相同的模式，R和S的差是由属于R但不属于S的元组构成的集合。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"4a3021b5-0e48-478b-8647-7e44e13417da","page_size":[595,841],"block_position":"30-1"},{"bbox":[91,157,204,169],"type":"text","angle":0,"index":2,"text":"R-S≡{t| t∈R ∧t 不属于 S}","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"82a22049-cc4c-4059-9d1d-e860f57cd0d9","page_size":[595,841],"block_position":"30-2"},{"bbox":[86,172,504,200],"type":"text","angle":0,"index":3,"text":"(3)笛卡尔积（×）：对两个关系R和S进行操作，产生的关系中元组个数为两个关系中元组个数之积。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"5bd9da6a-5479-4993-a98a-6ca081e42967","page_size":[595,841],"block_position":"30-3"},{"bbox":[91,204,227,216],"type":"text","angle":0,"index":4,"text":"R×S≡{t| t=< tr,ts>∧tr∈R∧ts ∈S}","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"fdc1d766-52cf-4f19-a524-7ce603088a97","page_size":[595,841],"block_position":"30-4"},{"bbox":[86,219,414,232],"type":"text","angle":0,"index":5,"text":"(4) 投影 $( \\pmb { \\pi } )$ ：对关系进行垂直分割，消去某些列，并重新安排列的顺序。","id":"4d8ecc5f-edc4-4c47-a207-33d932fd9693","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"page_size":[595,841],"block_position":"30-5"},{"bbox":[87,235,404,248],"type":"text","angle":0,"index":6,"text":"(5) 选择 $( \\pmb { \\sigma } )$ ：根据某些条件关系作水平分割，即选择符合条件的元组。","id":"939ed83d-d89c-4d2a-bea6-ebbadb47aa61","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"page_size":[595,841],"block_position":"30-6"},{"bbox":[87,250,373,263],"type":"text","angle":0,"index":7,"text":"1)交(∩)：R 和 S 的交是由既属于 R 又属于 S 的元组构成的集合。","id":"2a431e69-abe3-41bc-9ebb-5b5750d30284","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"page_size":[595,841],"block_position":"30-7"},{"bbox":[87,266,303,279],"type":"text","angle":0,"index":8,"text":"(2)连接:包括 θ(算术比较符)连接和 F(公式)连接.","id":"0ce69341-9bfa-426e-b552-0bf3f6099387","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"page_size":[595,841],"block_position":"30-8"},{"bbox":[88,281,322,294],"type":"text","angle":0,"index":10,"text":"选择 ${ \\sf R } { \\sf x } { \\sf S }$ 中满足 $\\mathsf { i } \\Theta ( \\mathsf { r } + \\mathsf { j } )$ 或 F 条件的元组构成的集合；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"68d6c9e6-ba2e-43ae-9bfe-0f3168166fb5","page_size":[595,841],"block_position":"30-9"},{"bbox":[86,297,268,310],"type":"text","angle":0,"index":11,"text":"概念上比较难理解，关键理解运算实例","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"a4119ec5-4efb-46af-b93d-d0a9679a1593","page_size":[595,841],"block_position":"30-10"},{"bbox":[86,312,233,326],"type":"text","angle":0,"index":12,"text":"等值连接(θ 为等号“=”的连接)。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"5dc85652-7e08-4de8-8baa-dad95fe815cd","page_size":[595,841],"block_position":"30-11"},{"bbox":[86,328,504,357],"type":"text","angle":0,"index":13,"text":"(3)自然连接(R S)：在 ${ \\sf R } { \\sf x } { \\sf S }$ 中，选择R和S公共属性值均相等的元组，并去掉 ${ \\sf R } { \\sf x } { \\sf S }$ 中重复的公共属性列。 如果两个关系没有公共属性，则自然连接就转化为笛卡尔积。","id":"ce109af7-f36d-4cc5-a51b-a29345c663ea","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"page_size":[595,841],"block_position":"30-12"},{"bbox":[87,359,327,373],"type":"text","angle":0,"index":14,"text":"(4)除法 $( \\div )$ ：首先除法的结果中元数为两个元数的差，","id":"e54c5f2d-072d-44d3-91b4-46f5e6663110","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"page_size":[595,841],"block_position":"30-13"},{"bbox":[99,382,508,426],"type":"text","angle":0,"index":16,"text":"$\\mathsf { R } { \\div } \\mathsf { S }$ 的操作思路如下---把S看作一个块，如果R中相同属性集中的元组有相同的块， 且除去此块后留下的相应元组均相同，那么可以得到一条元组， 所有这些元组的集合就是除法的结果","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"89b3f31e-42df-40b3-8fdd-4fb4fb855c71","page_size":[595,841],"block_position":"30-14"},{"bbox":[86,436,461,450],"type":"text","angle":0,"index":17,"text":"对于上述的五个基本操作和四个组合操作，应当从实际运算方面进行理解和运用。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"9154bf11-00d6-4cd0-9fb2-2c7cd4b30345","page_size":[595,841],"block_position":"30-15"},{"bbox":[86,467,136,481],"type":"text","angle":0,"index":18,"text":"应用举例：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"ea451875-4163-43ed-9de5-4cdc714051d3","page_size":[595,841],"block_position":"30-16"},{"bbox":[86,483,207,497],"type":"text","angle":0,"index":19,"text":"设有关系 R 和 S（如下：）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"fbdc52d1-5ea6-4ecf-9ace-6aca9713ec77","page_size":[595,841],"block_position":"30-17"},{"bbox":[94,506,186,584],"index":20,"angle":0,"type":"table_body","img_path":"/","id":"42f0dac7-851b-4cce-a0c2-5876cb195a02","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
RABC
367
257
723
443
","page_idx":30,"page_size":[595,841],"block_position":"30-18"},{"bbox":[201,507,303,555],"index":21,"angle":0,"type":"table_body","img_path":"/","id":"e620c693-d253-4fe6-ae01-736c187da3e3","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
S:ABC
345
723
","page_idx":30,"page_size":[595,841],"block_position":"30-19"},{"bbox":[87,608,116,621],"type":"text","angle":0,"index":22,"text":"计算：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":30,"id":"cc2cd2ea-949f-4969-8a58-2d0bb3edb31d","page_size":[595,841],"block_position":"30-20"}],[{"bbox":[94,123,123,139],"type":"text","angle":0,"index":1,"text":"RUS","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"2d434697-fdc7-40c1-b2d9-be2460b0b59d","page_size":[595,841],"block_position":"31-0"},{"bbox":[135,121,217,214],"index":2,"angle":0,"type":"table_body","img_path":"/","id":"e151104b-7884-4430-ba04-9a4b69419a66","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
ABC
367
257
723
443
345
","page_idx":31,"page_size":[595,841],"block_position":"31-1"},{"bbox":[248,119,352,190],"index":3,"angle":0,"type":"table_body","img_path":"/","id":"6a351112-c99c-47ec-8abb-3179e747c10d","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
R-SABC
367
257
443
","page_idx":31,"page_size":[595,841],"block_position":"31-2"},{"bbox":[375,131,402,147],"type":"text","angle":0,"index":4,"text":"Rns","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"f3be9d49-64ba-40d0-8174-ecf0e39bcaf7","page_size":[595,841],"block_position":"31-3"},{"bbox":[407,125,488,178],"index":5,"angle":0,"type":"table_body","img_path":"/","id":"0ffd58a1-e659-494d-8b87-c8d59aa90716","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
ABC
723
","page_idx":31,"page_size":[595,841],"block_position":"31-4"},{"bbox":[93,238,282,371],"index":6,"angle":0,"type":"table_body","img_path":"/","id":"0bf54d76-1b78-4d8f-8232-a1ee195d3df7","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
R×SR.AR.BR.CS.AS.BS.C
367345
367723
257345
257723
723345
723723
443345
443723
","page_idx":31,"page_size":[595,841],"block_position":"31-5"},{"bbox":[305,238,491,380],"index":7,"angle":0,"type":"table_body","img_path":"/","id":"6a6fed29-0877-49a4-8d56-f761eeba75a2","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
π3,2(S)σB<',5'(R)
CBABC
54723
32443
R×S2<2R.AR.BR.CS.AS.BS.C
723345
","page_idx":31,"page_size":[595,841],"block_position":"31-6"},{"bbox":[119,396,148,410],"type":"text","angle":0,"index":8,"text":"RXS.","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"e25befe5-0799-485b-b81c-3ff428a9555e","page_size":[595,841],"block_position":"31-7"},{"bbox":[160,394,240,438],"index":9,"angle":0,"type":"table_body","img_path":"/","id":"db1aba80-6278-425b-9a74-951bbda93ffa","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
ABC
723
","page_idx":31,"page_size":[595,841],"block_position":"31-8"},{"bbox":[86,468,504,497],"type":"text","angle":0,"index":10,"text":"有关实际应用，应该多看例题，多做习题，必须达到以下要求： 能够根据给出的关系代数表达式计算关系值，也能够根据相应查询要求列出关系表达式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"a65e314e-05be-41ef-89ac-ef97c0bb2c81","page_size":[595,841],"block_position":"31-9"},{"bbox":[93,500,289,512],"type":"text","angle":0,"index":11,"text":"（1）在列关系表达式时，通常有以下形式：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"e0870c1f-b5f3-4ac2-a0bb-c92fca2dab40","page_size":[595,841],"block_position":"31-10"},{"bbox":[86,516,229,528],"type":"text","angle":0,"index":12,"text":"$\\pi . . . ( \\sigma . . ( \\mathsf { R } { \\times } \\mathsf { S } ) )$ 或者 π...(σ...(R S))","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"174e33ec-1994-421b-8f42-15c346e6180f","page_size":[595,841],"block_position":"31-11"},{"bbox":[86,530,504,559],"type":"text","angle":0,"index":13,"text":"首先把查询涉及到的关系取来，执行笛卡尔积或自然连接操作得到一张大的表格，然后对大表格执行水平分割(选择)和垂直分割(投影)操作。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"4201ded7-7493-4380-b2a5-bbc5aeaf2141","page_size":[595,841],"block_position":"31-12"},{"bbox":[92,562,404,575],"type":"text","angle":0,"index":14,"text":"（2）当查询涉及到否定或全部的逻辑时，往往要用到差或除法操作。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"a15fa822-1649-4731-beca-b9e8cc744d88","page_size":[595,841],"block_position":"31-13"},{"bbox":[87,577,236,590],"type":"text","angle":0,"index":15,"text":"学生关系 S(SNO,SNAME,AGE,SEX)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"2b89e724-0ced-4001-8525-0dc7065d4551","page_size":[595,841],"block_position":"31-14"},{"bbox":[110,593,247,606],"type":"text","angle":0,"index":16,"text":"学习关系 SC(SNO,CNO,GRADE)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"879ef34d-a047-4b0e-9df6-8833eac18f51","page_size":[595,841],"block_position":"31-15"},{"bbox":[111,608,265,622],"type":"text","angle":0,"index":17,"text":"课程关系 C(CNO,CNAME,TEACHER)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"fa60b51a-110c-4ec9-9aa4-57af05ab50a3","page_size":[595,841],"block_position":"31-16"},{"bbox":[99,624,295,637],"type":"text","angle":0,"index":18,"text":"下面用关系代数表达式表达每个查询语句。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"bb1a0781-a4d8-4971-9535-72d3561cb423","page_size":[595,841],"block_position":"31-17"},{"bbox":[87,640,291,653],"type":"text","angle":0,"index":19,"text":"(1) 检索学习课程号为 C2 的学生学号与成绩。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"4d204fc6-3b3c-41d2-84a9-7f588aea90b3","page_size":[595,841],"block_position":"31-18"},{"bbox":[96,656,195,669],"type":"interline_equation","angle":0,"index":20,"text":"$$\n\\pi_ {\\mathrm {S N O}, \\text {G R A D E}} (\\sigma_ {\\mathrm {C N O} = ^ {\\prime} \\mathrm {C 2} ^ {\\prime}} (\\mathrm {S C}))\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":31,"id":"9c25409b-f6fb-4296-b022-e03d996b2051","page_size":[595,841],"block_position":"31-19"},{"bbox":[87,671,286,684],"type":"text","angle":0,"index":21,"text":"(2) 检索学习课程号为C2的学生学号与姓名","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"aa733cc2-5baa-41c6-b155-1cfda4783fc3","page_size":[595,841],"block_position":"31-20"},{"bbox":[93,687,209,700],"type":"interline_equation","angle":0,"index":22,"text":"$$\n\\pi_ {S N O, S N A M E} \\left(\\sigma_ {C N O = ^ {\\prime} C 2 ^ {\\prime}} (S \\times S C)\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":31,"id":"cefee2f2-fb1e-474e-bf2c-685e703f6c90","page_size":[595,841],"block_position":"31-21"},{"bbox":[86,702,504,730],"type":"text","angle":0,"index":23,"text":"由于这个查询涉及到两个关系S和SC，因此先对这两个关系进行自然连接，同一位学生的有关的信息，然后再执行选择投影操作。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"1ff49b73-1e1b-4ead-a083-23fe0135ad70","page_size":[595,841],"block_position":"31-22"},{"bbox":[87,734,199,746],"type":"text","angle":0,"index":24,"text":"此查询亦可等价地写成：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":31,"id":"c41d633e-1b07-488f-93f1-3c2612862ef2","page_size":[595,841],"block_position":"31-23"},{"bbox":[96,749,264,762],"type":"interline_equation","angle":0,"index":25,"text":"$$\n\\pi_ {\\text {S N O}, \\text {S N A M E}} (\\mathbf {s}) \\bowtie (\\pi_ {\\text {S N O}} (\\sigma_ {\\text {C N O} = ^ {\\prime} C 2 ^ {\\prime}} (\\text {S C})))\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":31,"id":"5eb17314-5706-43d6-a080-bc4242e19410","page_size":[595,841],"block_position":"31-24"}],[{"bbox":[86,79,505,107],"type":"text","angle":0,"index":0,"text":"这个表达式中自然连接的右分量为\"学了C2课的学生学号的集合\"。这个表达式比前一个表达式优化，执行起来要省时间，省空间。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"d9622072-345b-49bf-9eae-81c59eb260bb","page_size":[595,841],"block_position":"32-0"},{"bbox":[93,110,324,122],"type":"text","angle":0,"index":1,"text":"（3）检索选修课程名为 MATHS 的学生学号与姓名。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"81ea3d2f-5ebd-42b6-b64c-9160b7c01ca0","page_size":[595,841],"block_position":"32-1"},{"bbox":[96,126,246,139],"type":"interline_equation","angle":0,"index":2,"text":"$$\n\\pi_ {S N O, S A N M E} \\left(\\sigma_ {C N A M E = ^ {\\prime} M A T H S ^ {\\prime}} (S \\times S C \\times C)\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"01e8ddd3-8cbb-4ef3-a099-38a684d5c4f4","page_size":[595,841],"block_position":"32-2"},{"bbox":[94,141,298,153],"type":"text","angle":0,"index":3,"text":"（4）检索选修课程号为C2或C4的学生学号。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"f4348e46-2fe6-41fa-bb00-75e950563719","page_size":[595,841],"block_position":"32-3"},{"bbox":[96,157,199,169],"type":"interline_equation","angle":0,"index":4,"text":"$$\n\\pi_ {\\mathrm {S N O}} \\left(\\sigma_ {\\mathrm {C N O} = ^ {\\prime} \\mathrm {C 2} ^ {\\prime} \\mathrm {V} ^ {\\prime} \\mathrm {C N O} = ^ {\\prime} \\mathrm {C 4} ^ {\\prime}} (\\mathrm {S C})\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"46d82699-6dc5-4b1f-affa-446d9261534d","page_size":[595,841],"block_position":"32-4"},{"bbox":[94,172,321,185],"type":"text","angle":0,"index":5,"text":"（5） 检索至少选修课程号为 C2 或 C4 的学生学号。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"bda33f81-1ed0-4b70-bc3c-ffaf6f62e7fa","page_size":[595,841],"block_position":"32-5"},{"bbox":[96,188,218,201],"type":"interline_equation","angle":0,"index":6,"text":"$$\n\\pi_ {1} \\left(\\sigma_ {1 = 4 \\wedge 2 = ^ {\\prime} C 2 ^ {\\prime} \\wedge 5 = ^ {\\prime} C 4 ^ {\\prime}} (\\mathrm {S C} \\times \\mathrm {S C})\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"c5bd24ac-7065-4098-a04a-584b68005505","page_size":[595,841],"block_position":"32-6"},{"bbox":[86,203,504,232],"type":"text","angle":0,"index":7,"text":"这里（ $5 C { \\times } 5 C$ ）表示关系SC自身相乘的乘积操作，其中数字1，2，4，5都为它的结果关系中的属性序号。 这个大家理解即可，太绕了，可以用除法实现：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"858b9972-20a9-4b15-8695-3f13f095963d","page_size":[595,841],"block_position":"32-7"},{"bbox":[86,235,243,248],"type":"interline_equation","angle":0,"index":8,"text":"$$\n\\pi_ {\\mathrm {S N O}, \\mathrm {c n o}} (\\mathrm {S C}) \\div \\pi \\mathrm {c} _ {\\mathrm {N O}} \\left(\\sigma_ {\\mathrm {C N O} = ^ {\\prime} \\mathrm {C 2} ^ {\\prime}} \\mathrm {v C N O} = ^ {\\prime} \\mathrm {C 4} ^ {\\prime} (\\mathrm {S C})\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"afe0d018-9b6c-46da-875d-ce51b5b8c779","page_size":[595,841],"block_position":"32-8"},{"bbox":[93,250,274,263],"type":"text","angle":0,"index":9,"text":"（6） 检索不学C2课的学生姓名与年龄。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"e4707ece-6ba4-4d60-84cd-ea402537d025","page_size":[595,841],"block_position":"32-9"},{"bbox":[96,266,303,280],"type":"interline_equation","angle":0,"index":10,"text":"$$\n\\pi_ {\\text {S N A M E}, \\text {A G E}} (\\mathbf {s}) - \\pi_ {\\text {S N A M E}, \\text {A G E}} \\left(\\sigma_ {\\text {C N O} = ^ {\\prime} \\mathrm {C 2}} (\\mathbf {s} \\times \\mathbf {s c})\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"516b64af-68c0-4900-9282-e1d49b674efc","page_size":[595,841],"block_position":"32-10"},{"bbox":[86,281,505,310],"type":"text","angle":0,"index":11,"text":"这个表达式用了差运算，差运算的左分量为\"全体学生的姓名和年龄\"，右分量为\"学了C2课的学生姓名与年龄\"。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"dbb041a5-2a5a-4b95-a8f1-820bf6633e47","page_size":[595,841],"block_position":"32-11"},{"bbox":[93,312,257,326],"type":"text","angle":0,"index":12,"text":"（7）检索学习全部课程的学生姓名。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"910d0277-8fa7-420b-b06e-8b05ff9c3f79","page_size":[595,841],"block_position":"32-12"},{"bbox":[86,328,273,341],"type":"text","angle":0,"index":13,"text":"编写这个查询语句的关系代数过程如下：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"36c8baf1-d04d-4c76-8dfb-37876bc0c366","page_size":[595,841],"block_position":"32-13"},{"bbox":[87,343,262,357],"type":"text","angle":0,"index":14,"text":"(a) 学生选课情况可用 $\\pi _ { \\mathsf { S N O , C N O } } ( \\mathsf { S C } )$ 表示；","id":"652983b2-42f2-44c4-97b5-86d47f7636e3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"page_size":[595,841],"block_position":"32-14"},{"bbox":[88,359,224,373],"type":"text","angle":0,"index":15,"text":"(b) 全部课程可用 $\\pi _ { \\mathsf { C N O } } ( \\mathsf { C } )$ 表示；","id":"6b6622d3-ef2b-41dd-9a0f-f88d80b89fae","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"page_size":[595,841],"block_position":"32-15"},{"bbox":[87,375,307,388],"type":"text","angle":0,"index":16,"text":"(c) 学了全部课程的学生学号可用除法操作表示。","id":"6c05f169-861f-42cd-9b5a-6282bd335120","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"page_size":[595,841],"block_position":"32-16"},{"bbox":[86,391,505,434],"type":"text","angle":0,"index":18,"text":"操作结果为学号SNO的集合，该集合中每个学生（对应SNO)与C中任一门课程号CNO配在一起都在πSCO，CNO（SC） 中出现（即SC中出现），所以结果中每个学生都学了全部的课程（这是\"除法\"操作的含义）：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"b6fcef96-da20-41f7-8420-b72d40f7cd2a","page_size":[595,841],"block_position":"32-17"},{"bbox":[96,438,181,450],"type":"interline_equation","angle":0,"index":19,"text":"$$\n\\pi_ {\\mathrm {S N O}, \\mathrm {C N O}} (\\mathrm {S C}) \\div \\pi_ {\\mathrm {C N O}} (\\mathrm {C})\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"e831cc41-e5b7-479d-bf9c-ecd4a0d155d0","page_size":[595,841],"block_position":"32-18"},{"bbox":[87,453,406,465],"type":"text","angle":0,"index":20,"text":"(d) 从 SNO 求学生姓名 SNAME，可以用自然连结和投影操作组合而成：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"268e41d0-dc9d-4af4-abcd-d0185b2d959b","page_size":[595,841],"block_position":"32-19"},{"bbox":[96,469,236,481],"type":"interline_equation","angle":0,"index":21,"text":"$$\n\\pi_ {S N A M E} (S \\boxtimes (\\pi_ {S N O, C N O} (S C) \\div \\pi_ {C N O} (C)))\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"151ed804-b988-4729-813f-36b63283d291","page_size":[595,841],"block_position":"32-20"},{"bbox":[86,483,252,497],"type":"text","angle":0,"index":22,"text":"这就是最后得到的关系代数表达式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"b793811f-e9a6-4555-b2db-022f91ac7059","page_size":[595,841],"block_position":"32-21"},{"bbox":[93,500,315,512],"type":"text","angle":0,"index":23,"text":"（8） 检索所学课程包含S3所学课程的学生学号。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"24fbb05d-8d56-4456-ad07-bca3651d3093","page_size":[595,841],"block_position":"32-22"},{"bbox":[86,515,423,528],"type":"text","angle":0,"index":24,"text":"注意：学生S3可能学多门课程，所以要用到除法操作来表达此查询语句。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"9d60acd9-f888-40e7-9e44-dc35645763c6","page_size":[595,841],"block_position":"32-23"},{"bbox":[100,530,285,544],"type":"text","angle":0,"index":25,"text":"学生选课情况可用操作 πSNO,CNO(SC)表示；","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"39eb4eeb-5fc9-4f75-b3f9-68c09b747105","page_size":[595,841],"block_position":"32-24"},{"bbox":[100,546,406,560],"type":"text","angle":0,"index":26,"text":"所学课程包含学生S3所学课程的学生学号，可以用除法操作求得：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":32,"id":"96cbbd2c-92d1-40fc-9d5d-9ccb38dd2c10","page_size":[595,841],"block_position":"32-25"},{"bbox":[96,563,229,576],"type":"interline_equation","angle":0,"index":27,"text":"$$\n\\pi_ {\\mathrm {S N O}, \\mathrm {C N O}} (\\mathrm {S C}) \\div \\pi_ {\\mathrm {C N O}} \\left(\\sigma_ {\\mathrm {S N O} = ^ {\\prime} \\mathrm {S} ^ {\\prime}} (\\mathrm {S C})\\right)\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":32,"id":"2ffa01d0-3ba0-449c-bed0-3ef188f9ad73","page_size":[595,841],"block_position":"32-26"}],[{"bbox":[94,79,376,92],"type":"text","angle":0,"index":0,"text":"查询优化的目的就是为了系统在执行时既省时间又能提高效率。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"e2333992-f7e5-4249-8197-2e1959667aad","page_size":[595,841],"block_position":"33-0"},{"bbox":[94,95,498,123],"type":"text","angle":0,"index":1,"text":"在关系代数运算中，通常是先进行笛卡尔积或连接运算，再进行选择和投影。笛卡尔积或连接运算却往往花费教多的时间。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"5d9b4647-052e-4af8-8e90-d15b8cda01b4","page_size":[595,841],"block_position":"33-1"},{"bbox":[94,126,498,156],"type":"text","angle":0,"index":2,"text":"因此，恰当地安排选择、投影和连接的顺序直接影响到整个操作所需要的时间和空间。如何安排若干关系的运算操作步骤，是查询优化所要考虑的问题。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"b5e54c08-8246-4942-bca8-4be62e90ab68","page_size":[595,841],"block_position":"33-2"},{"bbox":[94,169,290,185],"type":"title","angle":0,"index":3,"text":"# 3.2关系代数表达式的等价变换规则","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":33,"id":"fc2ef5be-d062-43ff-a82c-a69cc5d1bfb8","page_size":[595,841],"block_position":"33-3"},{"bbox":[94,186,229,200],"type":"text","angle":0,"index":4,"text":"考核要求：达到”识记”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"61abe295-ebde-4bbd-bb29-9a4d85d8c5f5","page_size":[595,841],"block_position":"33-4"},{"bbox":[95,202,198,216],"type":"text","angle":0,"index":5,"text":"知识点：等价变换规则","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"3e2530a1-b86c-4cfb-a27f-67b4ce4d63c6","page_size":[595,841],"block_position":"33-5"},{"bbox":[94,234,493,264],"type":"text","angle":0,"index":6,"text":"两个关系代数表达式等价是指用同样的关系实例代替两个表达式中相应关系时所得到的结果是完全一样的。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"01c065f9-4fc5-4fcb-bca8-7b1d5e87260d","page_size":[595,841],"block_position":"33-6"},{"bbox":[110,266,330,280],"type":"text","angle":0,"index":7,"text":"等价变换规则有很多，不要死记，从语义上理解。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"39fdafbf-609c-435e-aacc-4efd79b1717a","page_size":[595,841],"block_position":"33-7"},{"bbox":[94,282,498,312],"type":"text","angle":0,"index":8,"text":"其实，只要在前面的学习中已经掌握关系运算的真正含义，就可以判断两个关系代数表达式是否等价。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"8e007564-6280-4c28-b53c-c653547a5fa6","page_size":[595,841],"block_position":"33-8"},{"bbox":[94,328,183,343],"type":"title","angle":0,"index":9,"text":"# 3.3优化的策略","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":33,"id":"f805a5a8-5401-4b4e-a0e3-93eb60b58ba8","page_size":[595,841],"block_position":"33-9"},{"bbox":[94,346,229,359],"type":"text","angle":0,"index":10,"text":"考核要求：达到”领会”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"13809ded-24e8-41c1-8e79-3fda780ef933","page_size":[595,841],"block_position":"33-10"},{"bbox":[95,362,248,375],"type":"text","angle":0,"index":11,"text":"知识点：优化的策略及其简单应用","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"c42af33c-a7af-40e1-bc5c-970ca2c3f874","page_size":[595,841],"block_position":"33-11"},{"bbox":[94,394,224,407],"type":"text","angle":0,"index":12,"text":"优化的策略主要有以下几点：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"d17b34a1-b4a7-4e53-b9d2-adb81cc187f0","page_size":[595,841],"block_position":"33-12"},{"bbox":[94,410,320,423],"type":"text","angle":0,"index":13,"text":"(1)在关系代数表达式中尽可能早地执行选择操作；","id":"3d654903-b24e-408e-a6ca-f6784c30fd64","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-13"},{"bbox":[94,426,329,439],"type":"text","angle":0,"index":14,"text":"(2)把笛卡尔积和随后的选择操作合并成F连接运算；","id":"568544ba-4821-4790-811c-10b0a8dc9675","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-14"},{"bbox":[95,442,270,454],"type":"text","angle":0,"index":15,"text":"(3)同时计算一连串的选择和投影操作；","id":"178b149b-1b0d-4475-9202-2d3885e04b9d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-15"},{"bbox":[95,458,230,470],"type":"text","angle":0,"index":16,"text":"（4)保留同一子表达式的结果；","id":"00988041-7996-4559-988b-bf7751b5ad46","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-16"},{"bbox":[95,474,244,486],"type":"text","angle":0,"index":17,"text":"(5)适当对关系文件进行预处理；","id":"117b61cf-6e29-44a0-ac60-f9e53eafe125","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-17"},{"bbox":[95,490,299,502],"type":"text","angle":0,"index":18,"text":"(6)计算表达式之前先估计一下怎么计算合算。","id":"f05a6fb4-7192-45d9-a817-944b80d3b0d4","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-18"},{"bbox":[94,521,415,534],"type":"text","angle":0,"index":20,"text":"以上优化策略要求会简单应用：先做选择，运用投影去除多余属性等等。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"4329be83-b922-4bdf-8a41-33ab94c1b213","page_size":[595,841],"block_position":"33-19"},{"bbox":[94,552,266,566],"type":"title","angle":0,"index":21,"text":"# 3.4关系代数表达式的优化算法","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":33,"id":"08038005-ea45-477d-a6b8-0824fb37c5e7","page_size":[595,841],"block_position":"33-20"},{"bbox":[94,569,248,582],"type":"text","angle":0,"index":22,"text":"考核要求：达到”简单应用”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"176c640b-6668-45df-b10c-6dcad52a7a3e","page_size":[595,841],"block_position":"33-21"},{"bbox":[95,586,168,598],"type":"text","angle":0,"index":23,"text":"知识点：语法树","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"3f963156-88a1-4cb9-bb34-379426bbccf0","page_size":[595,841],"block_position":"33-22"},{"bbox":[94,617,244,630],"type":"text","angle":0,"index":24,"text":"学会画语法树，并掌握优化算法。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"59c946a4-8f76-40e2-a4e3-78ee092f07c8","page_size":[595,841],"block_position":"33-23"},{"bbox":[95,649,117,661],"type":"title","angle":0,"index":25,"text":"# 举例","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":33,"id":"ff4fdcf2-2179-45e6-b857-fdc98ffd4ded","page_size":[595,841],"block_position":"33-24"},{"bbox":[94,667,500,681],"type":"text","angle":0,"index":26,"text":"在教学数据库S、SC`C中,用户有一查询语句：检索女同学选修课程的课程名和任课教师名。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"id":"e424538a-2b52-4c7b-a6ca-2dd3eb4e85ee","page_size":[595,841],"block_position":"33-25"},{"bbox":[94,686,259,698],"type":"text","angle":0,"index":27,"text":"（1)试写出该查询的关系代数表达式；","id":"86647830-1771-4c9f-ad76-3703fc1a0d41","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-26"},{"bbox":[94,703,270,716],"type":"text","angle":0,"index":28,"text":"(2)试写出查询优化的关系代数表达式；","id":"c9415df5-979e-421c-b6b1-3cf056a2a4b3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-27"},{"bbox":[94,721,309,734],"type":"text","angle":0,"index":29,"text":"(3)画出该查询初始的关系代数表达式的语法树；","id":"cb686d3a-c345-4d0d-b814-a6d63e351c80","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-28"},{"bbox":[94,739,430,752],"type":"text","angle":0,"index":30,"text":"(4)使用2.4.4节的优化算法，对语法树进行优化，并画出优化后的语法树。","id":"47f11b42-8009-4c91-9a64-2d4766d62b92","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":33,"page_size":[595,841],"block_position":"33-29"}],[{"bbox":[87,111,229,123],"type":"text","angle":0,"index":0,"text":"(1)πCNAME,TEACHER(σSEX='女'(S SC C))","id":"f03ee61e-1f17-41e6-898b-f90f9ea5f573","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"page_size":[595,841],"block_position":"34-0"},{"bbox":[87,126,338,139],"type":"text","angle":0,"index":1,"text":"(2)优化为： $\\pi _ { \\mathtt { C N A M E } , \\mathtt { \\tau _ { F E A C H E R } } } ( \\mathtt { C l } \\Join _ { \\mathtt { C } _ { \\# } } ( \\pi _ { \\mathtt { S } _ { \\# } , \\mathtt { C } _ { \\# } } ( \\mathsf { S C } ) \\lvert \\Join$","id":"01880566-bc57-4da3-a6d5-9c2afc14dad3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"page_size":[595,841],"block_position":"34-1"},{"bbox":[87,141,496,154],"type":"text","angle":0,"index":3,"text":"(基本思路：尽量提前做选择操作；在每个操作后，应做个投影操作，去掉不用的属性值。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"id":"9b482ca9-3462-40a8-ade6-868428b937ad","page_size":[595,841],"block_position":"34-2"},{"bbox":[128,161,274,366],"index":4,"angle":0,"type":"image","img_path":"/c5cf98588f1c817af21465451f17d7e9f054f7bca7a17b1c8e3429dea7fae0c5.jpg","color":{"line":"rgba(89, 92, 220, 1)","fill":"rgba(89, 92, 220, 1)"},"img_ratio":0.2453781512605042,"page_idx":34,"id":"02aa61c5-4ffc-42bb-b5b9-c5c01694b4bd","page_size":[595,841],"block_position":"34-3"},{"bbox":[305,158,451,384],"index":5,"angle":0,"type":"image","img_path":"/6131cc150d270daaf1dc47600b95b66abf7ade9afaefa725c74c406a4e9517c9.jpg","color":{"line":"rgba(89, 92, 220, 1)","fill":"rgba(89, 92, 220, 1)"},"img_ratio":0.2453781512605042,"page_idx":34,"id":"c63da01b-8324-427e-9817-9f642a859a16","page_size":[595,841],"block_position":"34-4"},{"bbox":[86,445,420,459],"type":"text","angle":0,"index":6,"text":"关系数据库是以关系模型为基础的数据库，它利用关系来描述现实世界。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"id":"e1a03b12-aebc-4684-8214-bc3eb26ee122","page_size":[595,841],"block_position":"34-5"},{"bbox":[86,461,503,506],"type":"text","angle":0,"index":7,"text":"一个关系既可以用来描述一个实体及其属性，也可以用来描述实体间的联系。 关系实质上就是一张二维表，表的行称为元组，列称为属性。 关系是元组的集合，关系模式就是这个元组集合的描述。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"id":"9b855a38-a620-48af-a579-32d42f71a99a","page_size":[595,841],"block_position":"34-6"},{"bbox":[86,508,503,537],"type":"text","angle":0,"index":8,"text":"关系模式是用来定义关系的， 一个关系数据库包含一组关系，也就是包含一组二维表，这些二维表结构体的集合就构成数据库的模式(也可以理解为数据库的结构)。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"id":"178c2ec8-1e72-4ad8-aa6d-f8fcf70cf381","page_size":[595,841],"block_position":"34-7"},{"bbox":[86,539,472,568],"type":"text","angle":0,"index":9,"text":"关系数据库设计理论包括三个方面内容：数据依赖、范式、模式设计（分解）方法。核心内容是数据依赖。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":34,"id":"94dcf077-c4e3-45b9-931b-3f9541b1ac23","page_size":[595,841],"block_position":"34-8"}],[{"bbox":[94,84,190,100],"type":"title","angle":0,"index":0,"text":"# 2函数依赖(FD","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":35,"id":"7811a4e8-7651-46e7-af95-7437b2fc61d5","page_size":[595,841],"block_position":"35-0"},{"bbox":[101,122,212,137],"type":"title","angle":0,"index":1,"text":"# 2.1 函数依赖的定义","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":35,"id":"fbc88f7e-cb0b-48aa-869f-57461997e63a","page_size":[595,841],"block_position":"35-1"},{"bbox":[101,139,235,153],"type":"text","angle":0,"index":2,"text":"考核要求：达到”领会”层次","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"9c4d7927-99d4-4dcc-b791-b860e1a3a2f3","page_size":[595,841],"block_position":"35-2"},{"bbox":[101,156,214,169],"type":"text","angle":0,"index":3,"text":"知识点：函数依赖的定义","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"4455bf68-fff9-4802-a550-5c318738677d","page_size":[595,841],"block_position":"35-3"},{"bbox":[100,187,506,232],"type":"text","angle":0,"index":4,"text":"设有关系模式R(A1,A2，...An)或简记为RUXY是U的子集，r是R的任一具体关系，如果对r的任意两个元组t1,t2,由t1[X]=t2[X导致t1[Y]=t2[Y],则称×函数决定Y,或Y函数依赖于×，记为X→Y。X→Y为模式R的一个函数依赖。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"8f35dc22-d8c5-495c-abca-68271a5ed343","page_size":[595,841],"block_position":"35-4"},{"bbox":[100,251,504,296],"type":"text","angle":0,"index":5,"text":"该定义理解如下：有一张设计好的二维表，×，Y是表的某些列（可以是一列，也可以是多列)，若在表中的第t1行，和第t2行上的×值相等，那么必有t1行和t2行上的Y值也相等，这就是说Y函数依赖于X。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"810f4150-f8bb-4850-a4ec-c53e3a606c87","page_size":[595,841],"block_position":"35-5"},{"bbox":[107,315,199,327],"index":6,"angle":0,"type":"table_caption","text":"比如，有如下二维表","id":"d21238ce-cae8-401d-a446-93bb9ee9aea5","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"page_size":[595,841],"block_position":"35-6"},{"bbox":[89,329,335,558],"index":7,"angle":0,"type":"table_body","img_path":"/","id":"f705a08e-ef3a-43a6-9079-c3b15811e17c","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
学号姓名成绩成绩等级
00001李里77C
00002丁力91A
00003李小红85B
00004马琳85B
00005王佳怡66D
00006胡林70C
.....................
","page_idx":35,"page_size":[595,841],"block_position":"35-7"},{"bbox":[93,560,514,587],"type":"text","angle":0,"index":8,"text":"在表中，凡成绩相同的，对应的“成绩等级\"也必是相同的，因此，“成绩等级\"函数依赖于\"成绩”。但是反过来则不成立。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"a960ca2f-3752-457e-8fed-d07af801af44","page_size":[595,841],"block_position":"35-8"},{"bbox":[93,606,513,634],"type":"text","angle":0,"index":10,"text":"(1)在这张表中，任何一行的关系均应符合函数依赖的条件，如果有一行不符合函数依赖的条件，则函数依赖对于这个关系就不成立。","id":"b1f3debd-64ba-43b0-a4f8-bc4ed95e3f99","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"page_size":[595,841],"block_position":"35-9"},{"bbox":[94,637,380,650],"type":"text","angle":0,"index":11,"text":"(2)函数依赖是否成立是不可证明的，只能通过属性的含义来判断.","id":"45823d4b-216f-47d5-9222-e4afe75aa438","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"page_size":[595,841],"block_position":"35-10"},{"bbox":[86,687,220,699],"type":"text","angle":0,"index":13,"text":"码是唯一标识实体的属性集。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"097e57a4-cac3-47e6-beb6-5002c684d390","page_size":[595,841],"block_position":"35-11"},{"bbox":[86,702,273,714],"type":"text","angle":0,"index":14,"text":"码和函数依赖的关系满足以下两个条件：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"198258d5-001b-4d78-a511-f46be6e9192c","page_size":[595,841],"block_position":"35-12"},{"bbox":[86,717,447,745],"type":"text","angle":0,"index":15,"text":"设关系模式R(A1,A2...An)，F是R上的函数依赖集，X是R的一个子集，如果(1)X→A1A2...An∈F+","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"b688afda-c6b9-4b96-8330-29bd961e1e2d","page_size":[595,841],"block_position":"35-13"},{"bbox":[92,749,224,762],"type":"text","angle":0,"index":16,"text":"(X能够决定唯一的一个元组)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":35,"id":"305f0636-1a01-429c-bf97-5ec5e6ca461d","page_size":[595,841],"block_position":"35-14"}],[{"bbox":[86,79,307,92],"type":"text","angle":0,"index":0,"text":"(2)不存在 X 的真子集 Y，使得 Y→A1A2...An 成立","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"727d0522-bf4b-4fac-afbf-86a4dad0d55f","page_size":[595,841],"block_position":"36-0"},{"bbox":[91,95,273,107],"type":"text","angle":0,"index":1,"text":"(X 能满足（1）但又没有多余的属性集）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"b7fb2e7c-7b23-4ead-8985-a3e00117b5c4","page_size":[595,841],"block_position":"36-1"},{"bbox":[86,110,208,122],"type":"text","angle":0,"index":2,"text":"则 X 就是 R 的一个候选码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"239bdb5e-2c0a-42b8-b251-70bdb5d90914","page_size":[595,841],"block_position":"36-2"},{"bbox":[86,125,504,154],"type":"text","angle":0,"index":3,"text":"包含在任何一个候选码中的属性称为主属性，不包含在任何码中的属性为非主属性(非码属性)， 注意主属性应当包含在候选码中（只需要出现在一个候选码中就是主属性）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"7cfdfe00-2cd1-48c5-87ad-87c43bd401a7","page_size":[595,841],"block_position":"36-3"},{"bbox":[87,157,460,169],"type":"text","angle":0,"index":4,"text":"1NF：第一范式——即关系模式中的属性的值域中每一个值都是不可再分解的值。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"a56af225-101c-43df-b72c-c62c84767ab1","page_size":[595,841],"block_position":"36-4"},{"bbox":[86,172,495,185],"type":"text","angle":0,"index":5,"text":"如果某个数据库模式都是第一范式的，则称该数据库模式是属于第一范式的数据库模式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"4db6a32c-dcc5-4145-a9d1-296526b4fbc9","page_size":[595,841],"block_position":"36-5"},{"bbox":[86,188,499,217],"type":"text","angle":0,"index":6,"text":"如果关系模式R为第一范式，并且R中每一个非主属性完全函数依赖于R的某个候选码，则称为第二范式模式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"82356865-3e9f-4dca-b598-af7266c2cf3a","page_size":[595,841],"block_position":"36-6"},{"bbox":[86,234,472,248],"type":"text","angle":0,"index":7,"text":"首先温习、理解“非主属性”、“完全函数依赖”、“候选码”这三个名词的含义。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"2e669db2-a72e-4492-99d8-28d6aef593fd","page_size":[595,841],"block_position":"36-7"},{"bbox":[93,250,456,263],"type":"text","angle":0,"index":8,"text":"（1）候选码：可以唯一决定关系模式R中某元组值且不含有多余属性的属性集。","id":"8d76a6ad-b081-46ed-b224-58a1cb0d28e4","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"page_size":[595,841],"block_position":"36-8"},{"bbox":[93,266,424,279],"type":"text","angle":0,"index":9,"text":"（2）非主属性：即非码属性，指关系模式 R 中不包含在任何建中的属性。","id":"cbf3601c-5243-4256-8431-a1f722a79d8d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"page_size":[595,841],"block_position":"36-9"},{"bbox":[86,281,504,310],"type":"text","angle":0,"index":10,"text":"（3）完全函数依赖：设有函数依赖 ${ \\mathsf { W } } { \\to } \\mathsf { A }$ ，若存在 $\\mathsf { x } \\mathsf { \\subseteq } _ { \\mathsf { W } }$ ，有 $\\mathsf { X } { \\to } \\mathsf { A }$ 成立，那么称 ${ \\mathsf { W } } { \\to } \\mathsf { A }$ 是局部依赖，否则就称 ${ \\mathsf { W } } { \\to } \\mathsf { A }$ 是完全函数依赖。","id":"907e2e67-e392-4938-ae14-3812a5365c35","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"page_size":[595,841],"block_position":"36-10"},{"bbox":[86,312,504,341],"type":"text","angle":0,"index":12,"text":"如果关系模式R是第二范式，且每个非主属性都不传递依赖于R的候选码，则称R为第三范式模式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"ec9e547b-b583-4823-9236-5e9619acdb2e","page_size":[595,841],"block_position":"36-11"},{"bbox":[86,343,504,373],"type":"text","angle":0,"index":13,"text":"传递依赖的含义： 在关系模式中，如果 $\\mathsf { Y } { \\to } \\mathsf { X }$ ， $\\mathsf { X } { \\to } \\mathsf { A }$ ，且 X Y(X 不决定 Y)和 A X(A 不属于X)，那么 $\\mathsf { Y } { \\to } \\mathsf { A }$ 是传递依赖。 Notice:要求非主属性都不传递依赖于候选码。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"8e450190-4140-4845-bd70-ce597a710cc3","page_size":[595,841],"block_position":"36-12"},{"bbox":[86,390,451,403],"type":"text","angle":0,"index":14,"text":"上一小节例子中student（学号，姓名），study（学号，课程，成绩）都是3NF","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"7a6e263f-d57f-487f-ad6d-2a38bdc70143","page_size":[595,841],"block_position":"36-13"},{"bbox":[86,406,325,419],"type":"text","angle":0,"index":15,"text":"这个范式和第三范式有联系，它是 3NF 的改进形式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"b76e2eea-7475-49d8-aceb-8df431d2f53b","page_size":[595,841],"block_position":"36-14"},{"bbox":[86,422,504,449],"type":"text","angle":0,"index":16,"text":"若关系模式 R是第一范式，且每个属性都不传递依赖于 R的候选码。这种关系模式就是BCNF 模式。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"ef7aee16-d1ca-4f74-b715-a0641cfd9d49","page_size":[595,841],"block_position":"36-15"},{"bbox":[87,453,294,465],"type":"text","angle":0,"index":17,"text":"四种范式，可以发现它们之间存在如下关系：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"be429b58-6cb3-4676-95cb-de33d68b2734","page_size":[595,841],"block_position":"36-16"},{"bbox":[107,467,210,481],"type":"interline_equation","angle":0,"index":18,"text":"$$\n\\mathrm {B C N F} \\subseteq 3 \\mathrm {N F} \\subseteq 2 \\mathrm {N F} \\subseteq 1 \\mathrm {N F}\n$$","color":{"line":"rgba(230, 122, 171, 1)","fill":"rgba(230, 122, 171, 1)"},"page_idx":36,"id":"b3e31bc8-14d3-4c0d-947e-3c90bf393569","page_size":[595,841],"block_position":"36-17"},{"bbox":[262,489,280,499],"type":"text","angle":0,"index":19,"text":"1NF","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"ee49510c-e78f-42fc-b982-30235e9f36a3","page_size":[595,841],"block_position":"36-18"},{"bbox":[282,512,476,524],"type":"text","angle":0,"index":20,"text":"↓ 消去非主属性对码的部分函数依赖","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"c21985a0-1d65-41db-a5a4-a93be82693ec","page_size":[595,841],"block_position":"36-19"},{"bbox":[261,535,280,545],"type":"text","angle":0,"index":21,"text":"2NF","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"e0780375-7e39-4011-8253-0eac0e694c4f","page_size":[595,841],"block_position":"36-20"},{"bbox":[282,558,476,571],"type":"text","angle":0,"index":22,"text":"↓ 消去非主属性对码的传递函数依赖","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"9c756e41-e522-4477-b6e2-325554331a47","page_size":[595,841],"block_position":"36-21"},{"bbox":[262,581,280,592],"type":"text","angle":0,"index":23,"text":"3NF","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"b797dc0e-d9a3-4e7b-998f-ab881e9058ca","page_size":[595,841],"block_position":"36-22"},{"bbox":[282,604,465,617],"type":"text","angle":0,"index":24,"text":"↓ 消去主属性对码的传递函数依赖","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"278d301e-9212-4005-9e09-a4055d9f373d","page_size":[595,841],"block_position":"36-23"},{"bbox":[261,629,286,638],"type":"text","angle":0,"index":25,"text":"BCNF","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"4e7a839e-71d1-4187-b1ac-4f6581b924b7","page_size":[595,841],"block_position":"36-24"},{"bbox":[87,648,129,660],"type":"title","angle":0,"index":26,"text":"# SQL 语言","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":36,"id":"e95e0394-e1af-4262-acfb-292ea0d2b6d1","page_size":[595,841],"block_position":"36-25"},{"bbox":[87,663,291,677],"type":"title","angle":0,"index":27,"text":"# 数据定义语言 DDL (Data Definition Language)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":36,"id":"d1f17a5e-cad0-4aab-8107-78b7601c7a08","page_size":[595,841],"block_position":"36-26"},{"bbox":[88,679,409,723],"type":"text","angle":0,"index":28,"text":"用于创建、更改或删除数据库对象，如包括定义 Database, Table, View,Index,完整性约束条件等，也包括定义对象(RowType行对象, Type列对象)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"7afff9a0-3417-4e54-a377-5fdbb61c6387","page_size":[595,841],"block_position":"36-27"},{"bbox":[89,725,369,739],"type":"text","angle":0,"index":29,"text":"语句包括：CREATE（建立）、ALTER（修改）、DROP（撤销）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":36,"id":"d8b6dd14-1a23-408f-85ec-aa8536baf355","page_size":[595,841],"block_position":"36-28"},{"bbox":[88,743,95,751],"type":"page_number","angle":0,"index":1000029,"text":"v","color":{"line":"rgba(164, 164, 164, 1)","fill":"rgba(164, 164, 164, 1)"},"page_idx":36,"is_discarded":true,"id":"bbc5586d-f84f-403f-8989-a0f79a4b20e0","page_size":[595,841],"block_position":"36-29"}],[{"bbox":[87,79,309,92],"type":"title","angle":0,"index":0,"text":"# 数据操纵语言 DML (Data Manipulation Language)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":37,"id":"30da3275-7639-49d7-9f8c-300c6f6ec9ac","page_size":[595,841],"block_position":"37-0"},{"bbox":[89,95,234,107],"type":"text","angle":0,"index":1,"text":"用于操纵数据库对象（如表）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"39c59fd1-2b70-4e0e-891a-5d2479f460e5","page_size":[595,841],"block_position":"37-1"},{"bbox":[87,110,480,122],"type":"text","angle":0,"index":2,"text":"ü 各种方式的更新与检索操作，如直接输入记录，从其他 Table(由 SubQuery 建立)输入","id":"3ff37352-de20-44b3-8aad-1cc75e8a7b4a","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"page_size":[595,841],"block_position":"37-2"},{"bbox":[88,125,424,138],"type":"text","angle":0,"index":3,"text":"ü 各种复杂条件的检索，如连接查找，模糊查找，分组查找，嵌套查找等","id":"c2039bbe-973c-44db-9d10-93f9b2ca3646","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"page_size":[595,841],"block_position":"37-3"},{"bbox":[88,142,382,154],"type":"text","angle":0,"index":4,"text":"ü 各种聚集操作，求平均、求和、…等，分组聚集，分组过滤等","id":"b6395413-9ccd-4197-879c-f296d4639226","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"page_size":[595,841],"block_position":"37-4"},{"bbox":[89,157,304,169],"type":"text","angle":0,"index":6,"text":"语句包括：SELECT、INSERT、UPDATE、DELETE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"d0d5145b-a134-4582-b776-96e457d3923c","page_size":[595,841],"block_position":"37-5"},{"bbox":[88,174,95,183],"type":"text","angle":0,"index":7,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"dbf50b40-abe8-41d7-be3a-357757fea3c6","page_size":[595,841],"block_position":"37-6"},{"bbox":[87,188,279,201],"type":"title","angle":0,"index":8,"text":"# 数据控制语言 DCL (Data Control Language)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":37,"id":"7e1ed27e-7119-4d3e-8e58-7b51aeb3b4a3","page_size":[595,841],"block_position":"37-7"},{"bbox":[89,203,244,216],"type":"text","angle":0,"index":9,"text":"用于定义控制访问对象（如表）。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"7cb181b4-a77b-48e1-8cef-890a9eb271af","page_size":[595,841],"block_position":"37-8"},{"bbox":[87,219,234,232],"type":"text","angle":0,"index":10,"text":"v 安全性控制：授权和撤消授权","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"4be8573f-ec20-4ed9-acb5-7c1fef742aa1","page_size":[595,841],"block_position":"37-9"},{"bbox":[89,235,222,247],"type":"text","angle":0,"index":11,"text":"语句包括：GRANT、REVOKE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"31b10e5f-8ced-4dca-b554-ef23a9a3542b","page_size":[595,841],"block_position":"37-10"},{"bbox":[87,250,287,263],"type":"text","angle":0,"index":12,"text":"SQL的数据定义语句（DDL）包括以下语句：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"6653ac9b-4ea6-451f-b4c6-4623eff87f48","page_size":[595,841],"block_position":"37-11"},{"bbox":[88,266,158,279],"type":"text","angle":0,"index":13,"text":"创建 删除 修改","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"d66b6525-839b-4d15-92fc-dd821028bc08","page_size":[595,841],"block_position":"37-12"},{"bbox":[87,282,273,294],"type":"text","angle":0,"index":14,"text":"表 CTEATE TABLE DROP TABLE ALTER TABLE","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"1ddf0c96-9959-4531-9e4d-8124210c86fb","page_size":[595,841],"block_position":"37-13"},{"bbox":[87,297,276,310],"type":"text","angle":0,"index":15,"text":"视图 CTEATE VIEW DROP VIEW ALTER VIEW","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"7741c909-60e2-4d10-a9c6-fcc32340c7a7","page_size":[595,841],"block_position":"37-14"},{"bbox":[87,313,230,325],"type":"text","angle":0,"index":16,"text":"索引 CTEATE INDEX DROP INDEX","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"b1d67770-565d-4d74-97ec-92c192734fe6","page_size":[595,841],"block_position":"37-15"},{"bbox":[87,328,208,341],"type":"text","angle":0,"index":17,"text":"n 注意：索引无修改语句！","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"32f60c64-bf42-4eef-ac3c-7f19ea3cc89a","page_size":[595,841],"block_position":"37-16"},{"bbox":[87,359,155,372],"type":"title","angle":0,"index":18,"text":"# 创建 Database","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":37,"id":"9330cdb7-b5dc-474f-bbcb-bd03574c4090","page_size":[595,841],"block_position":"37-17"},{"bbox":[87,375,403,388],"type":"text","angle":0,"index":19,"text":"$\\varnothing$ 数据库(Database)是若干具有相互关联关系的 Table/Relation 的集合","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"defaa195-089f-423d-958e-aece0189ee0c","page_size":[595,841],"block_position":"37-18"},{"bbox":[88,391,348,403],"type":"text","angle":0,"index":20,"text":"$\\varnothing$ 数据库可以看作是一个集中存放若干 Table 的大型文件","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"1d9ea730-2a6b-4dd0-b7c1-613777b841b4","page_size":[595,841],"block_position":"37-19"},{"bbox":[87,407,246,418],"type":"text","angle":0,"index":21,"text":"Øcreate database 的简单语法形式：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"37631e61-0755-4e69-aee5-374177f4444e","page_size":[595,841],"block_position":"37-20"},{"bbox":[87,423,118,433],"type":"text","angle":0,"index":22,"text":"create","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"7341fd72-9f69-4ba9-bdbc-d536cd51c7fe","page_size":[595,841],"block_position":"37-21"},{"bbox":[87,438,131,449],"type":"text","angle":0,"index":23,"text":"database","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"64595f22-f23b-4b96-83ae-692fc94b7f09","page_size":[595,841],"block_position":"37-22"},{"bbox":[87,453,135,465],"type":"text","angle":0,"index":24,"text":"数据库名;","color":{"line":"rgba(13, 83, 222, 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83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"db1e0bc6-ee09-41b7-b959-f1401f4766e3","page_size":[595,841],"block_position":"37-30"},{"bbox":[88,593,201,606],"type":"text","angle":0,"index":32,"text":"n SQLCA是一个数据结构","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"50ce5d3a-4e85-47c1-8d77-d8f8ed6f3a7e","page_size":[595,841],"block_position":"37-31"},{"bbox":[88,610,95,619],"type":"text","angle":0,"index":33,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"f35afbf1-6819-4f56-8fed-ac75b84f1cb0","page_size":[595,841],"block_position":"37-32"},{"bbox":[87,624,152,637],"type":"text","angle":0,"index":34,"text":"SQLCA 的用途","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"d3434a45-a7fd-47e0-b050-cf06cb527097","page_size":[595,841],"block_position":"37-33"},{"bbox":[87,640,307,652],"type":"text","angle":0,"index":35,"text":"n SQL语句执行后，RDBMS反馈给应用程序信息","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"c6bce703-d377-44d5-8249-7a4bc84321e1","page_size":[595,841],"block_position":"37-34"},{"bbox":[88,655,205,667],"type":"text","angle":0,"index":36,"text":"$\\varnothing$ 描述系统当前工作状态","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"4ac5bca3-ec8a-47ed-bd83-1e4a53d3eed0","page_size":[595,841],"block_position":"37-35"},{"bbox":[88,671,163,683],"type":"text","angle":0,"index":37,"text":"$\\varnothing$ 描述运行环境","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"b21c2528-8c25-4c62-86b0-fc6910361616","page_size":[595,841],"block_position":"37-36"},{"bbox":[87,687,266,699],"type":"text","angle":0,"index":38,"text":"n 这些信息将送到 SQL 通信区 SQLCA 中","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"d51974c1-4e4e-4aab-9317-b36646954a79","page_size":[595,841],"block_position":"37-37"},{"bbox":[87,702,351,714],"type":"text","angle":0,"index":39,"text":"n 应用程序从 SQLCA 中取出这些状态信息，据此决定接下","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"49e14e04-65b2-40fd-abf3-761411df7cc1","page_size":[595,841],"block_position":"37-38"},{"bbox":[87,718,153,730],"type":"text","angle":0,"index":40,"text":"来执行的语句","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"d36a58e3-ded6-425c-a543-b2b39a7b0bfd","page_size":[595,841],"block_position":"37-39"},{"bbox":[87,749,132,761],"type":"text","angle":0,"index":41,"text":"存储过程","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":37,"id":"10e6ec81-6a69-413f-8994-3e201b61d560","page_size":[595,841],"block_position":"37-40"}],[{"bbox":[86,79,273,91],"type":"text","angle":0,"index":0,"text":"存储过程（Procedure）是一组为了完成","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"1c467dcd-e0de-4258-adb6-146e598eaf8f","page_size":[595,841],"block_position":"38-0"},{"bbox":[87,95,279,107],"type":"text","angle":0,"index":1,"text":"特定功能的SQL语句集，经编译后存储在","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"0e164f06-42fd-4c54-a038-8a1b7d4de502","page_size":[595,841],"block_position":"38-1"},{"bbox":[88,110,273,122],"type":"text","angle":0,"index":2,"text":"数据库中，可供应用程序在需要时调用。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"9d143986-6240-46b9-8bda-a205a1106306","page_size":[595,841],"block_position":"38-2"},{"bbox":[88,125,258,138],"type":"text","angle":0,"index":3,"text":"允许模块化程序设计，含有控制语句","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"a6fb6f4d-cd64-471b-bbd6-dde122e58193","page_size":[595,841],"block_position":"38-3"},{"bbox":[88,142,248,153],"type":"text","angle":0,"index":4,"text":"存储过程能够实现较快的执行速度","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"56698f6f-268b-4da9-ac23-888d126798c2","page_size":[595,841],"block_position":"38-4"},{"bbox":[88,157,216,169],"type":"text","angle":0,"index":5,"text":"存储过程能够减少网络流量","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"e5d113b8-5e87-4f2c-b7f4-aa7031a72ff8","page_size":[595,841],"block_position":"38-5"},{"bbox":[88,173,289,185],"type":"text","angle":0,"index":6,"text":"存储过程可被作为一种安全机制来充分利用","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"2d4e7081-c813-4a84-b660-25fc3410823c","page_size":[595,841],"block_position":"38-6"},{"bbox":[88,188,195,200],"type":"text","angle":0,"index":7,"text":"带参数的存储过程举例","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"ccd5a242-d839-47fd-bf9e-cfe56b734f69","page_size":[595,841],"block_position":"38-7"},{"bbox":[88,204,252,216],"type":"text","angle":0,"index":8,"text":"CREATE PROCEDURE pro_student_sno","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"567fe2ec-8cb9-4d58-b725-fea36052b570","page_size":[595,841],"block_position":"38-8"},{"bbox":[88,220,170,232],"type":"text","angle":0,"index":9,"text":"@givensno char(7)","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"c789aaa2-f7c8-4508-89dc-d26fa95fc504","page_size":[595,841],"block_position":"38-9"},{"bbox":[88,236,101,245],"type":"text","angle":0,"index":10,"text":"AS","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"d2492404-231e-4783-a562-aae44eeaf9b8","page_size":[595,841],"block_position":"38-10"},{"bbox":[88,250,168,261],"type":"text","angle":0,"index":11,"text":"SELECT sno,sname","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"c8f70390-4f57-4129-b408-bb372d810a7a","page_size":[595,841],"block_position":"38-11"},{"bbox":[88,266,152,277],"type":"text","angle":0,"index":12,"text":"FROM student","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"bbe16c0f-f0a7-4ad8-be93-0ffc2a996575","page_size":[595,841],"block_position":"38-12"},{"bbox":[88,282,195,294],"type":"text","angle":0,"index":13,"text":"WHERE sno=@givensno;","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"98fed76f-29a9-4792-b45d-287f39851dcd","page_size":[595,841],"block_position":"38-13"},{"bbox":[88,297,119,309],"type":"text","angle":0,"index":14,"text":"n 执行","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"0d9b18f8-19cd-4b34-aa20-d278e118f083","page_size":[595,841],"block_position":"38-14"},{"bbox":[88,313,285,325],"type":"text","angle":0,"index":15,"text":"EXEC pro_student_sno $@$ givensno $= ^ { 1 }$ 2000101'","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"6190b02d-0ee1-49e1-88bc-f3f9ac64fee5","page_size":[595,841],"block_position":"38-15"},{"bbox":[88,330,238,341],"type":"text","angle":0,"index":16,"text":"EXEC pro_student_sno '2000101';、","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"91c43254-d61e-404c-9c79-90b8e2f820ab","page_size":[595,841],"block_position":"38-16"},{"bbox":[87,359,304,372],"type":"text","angle":0,"index":17,"text":"可授权的数据对象：数据库、模式（全局模式、","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"b601d472-a2bc-4208-bbbd-7afe011f5103","page_size":[595,841],"block_position":"38-17"},{"bbox":[88,375,220,387],"type":"text","angle":0,"index":18,"text":"外模式），数据（表、属性）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"6893ac57-7c28-47d0-a7f5-59c62ab69e0b","page_size":[595,841],"block_position":"38-18"},{"bbox":[88,391,168,402],"type":"text","angle":0,"index":19,"text":"可以授权的操作：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"ceb358f0-5f11-4697-909a-5606abfdafda","page_size":[595,841],"block_position":"38-19"},{"bbox":[88,406,216,418],"type":"text","angle":0,"index":20,"text":"数据库的建立、删除、连接","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"7649f32b-1875-4719-b130-e313af206702","page_size":[595,841],"block_position":"38-20"},{"bbox":[88,422,206,434],"type":"text","angle":0,"index":21,"text":"模式的建立、修改、检索","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"277efde7-996a-4082-b28e-790b3df2eda2","page_size":[595,841],"block_position":"38-21"},{"bbox":[88,438,206,449],"type":"text","angle":0,"index":22,"text":"数据的建立、检索、修改","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"531ebddc-a541-43b5-bf5f-3662b5f3ca88","page_size":[595,841],"block_position":"38-22"},{"bbox":[88,453,168,465],"type":"text","angle":0,"index":23,"text":"对应的 SQL 语句：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"ffe40843-b5d5-4312-bbb5-efee09c092d0","page_size":[595,841],"block_position":"38-23"},{"bbox":[88,469,286,481],"type":"text","angle":0,"index":24,"text":"GRANT, REVOKE，数据库安全性控制是属于","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"2983adc8-0c17-419c-b993-5017457dcbe5","page_size":[595,841],"block_position":"38-24"},{"bbox":[88,485,134,497],"type":"text","angle":0,"index":25,"text":"DCL范畴。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"c3a50930-a0b6-44be-b179-96ac978c0f35","page_size":[595,841],"block_position":"38-25"},{"bbox":[87,499,504,528],"type":"text","angle":0,"index":26,"text":"可以结合视图加强对数据库存取的控制GRANT命令：把权限授予某一用户，以允许该用户执行针","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"85af9400-e959-476e-bde3-784ba56c6d1b","page_size":[595,841],"block_position":"38-26"},{"bbox":[88,530,273,543],"type":"text","angle":0,"index":27,"text":"对该对象的操作或允许其运行某些语句。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"7845f516-f2ef-4213-9cb5-2fa68b6b2af9","page_size":[595,841],"block_position":"38-27"},{"bbox":[88,546,368,575],"type":"text","angle":0,"index":28,"text":"REVOKE命令：用来撤销用户对某一对象或语句的权限，使其不能执行操作，除非该用户是角色成员，且角色被授权。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"7cda0f87-e717-46f5-85cc-fac0f2722d1d","page_size":[595,841],"block_position":"38-28"},{"bbox":[88,577,374,590],"type":"text","angle":0,"index":29,"text":"DENY 命令：用来禁止用户对某一对象或语句的权限，它不","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":38,"id":"e4dc06be-d067-4986-90f9-8f50005b50eb","page_size":[595,841],"block_position":"38-29"},{"bbox":[88,593,374,621],"type":"text","angle":0,"index":30,"text":"允许该用户执行针对数据库对象的某些操作或不允许其运行某些语句。对象","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 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1)"},"page_idx":40,"id":"7d599927-707e-4807-8881-67c160af8994","page_size":[595,841],"block_position":"40-15"},{"bbox":[88,375,179,387],"type":"text","angle":0,"index":16,"text":"将其属性分为4类：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"dd889ebe-4116-4d54-aa95-3d74cab76ffe","page_size":[595,841],"block_position":"40-16"},{"bbox":[87,391,264,402],"type":"text","angle":0,"index":17,"text":"L 类： 仅出现在 F 函数依赖左部的属性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"b708cae4-be77-4647-ac44-df4f8fba7198","page_size":[595,841],"block_position":"40-17"},{"bbox":[87,407,265,418],"type":"text","angle":0,"index":18,"text":"R 类： 仅出现在 F 函数依赖右部的属性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"815405e2-d9a1-418d-9f9b-53131f74770b","page_size":[595,841],"block_position":"40-18"},{"bbox":[87,422,309,433],"type":"text","angle":0,"index":19,"text":"N类： 在F函数依赖的左右两部均未出现的属性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"d606bed0-7469-45e4-bcb7-d0741eafb416","page_size":[595,841],"block_position":"40-19"},{"bbox":[87,438,301,449],"type":"text","angle":0,"index":20,"text":"LR类： 在F函数依赖的左右两部均出现的属性","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"11053d33-63e0-4d00-8a14-99c331147868","page_size":[595,841],"block_position":"40-20"},{"bbox":[88,455,95,463],"type":"text","angle":0,"index":21,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"dbf1bac6-72c3-4c56-8734-153904ed2447","page_size":[595,841],"block_position":"40-21"},{"bbox":[87,468,336,481],"type":"text","angle":0,"index":22,"text":"定理：对于给定的关系模式R及其函数依赖集F，若×","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"7ff0d680-557b-4fc4-a101-e44480e51b1d","page_size":[595,841],"block_position":"40-22"},{"bbox":[88,484,322,497],"type":"text","angle":0,"index":23,"text":"是R的L类属性，则X必为R的任一侯选码的成员。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"a8c4c3cb-ef8b-48c4-a315-5b25693f0a8d","page_size":[595,841],"block_position":"40-23"},{"bbox":[88,502,95,509],"type":"text","angle":0,"index":24,"text":"v","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"662e5f7e-b9c5-439d-a029-85c652b91341","page_size":[595,841],"block_position":"40-24"},{"bbox":[87,515,336,528],"type":"text","angle":0,"index":25,"text":"推论：对于给定的关系模式R及其函数依赖集F，若x","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"ccfd0f7b-1838-4507-8230-898d544df7aa","page_size":[595,841],"block_position":"40-25"},{"bbox":[87,531,349,543],"type":"text","angle":0,"index":26,"text":"是R的L类属性， $^ { \\mathbf { \\nabla } _ { E } \\times + }$ 包含了R的全部属性，则×必为R","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"44779c66-e8e8-43ff-a30b-22abedbb3348","page_size":[595,841],"block_position":"40-26"},{"bbox":[88,547,154,559],"type":"text","angle":0,"index":27,"text":"的唯一侯选码","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":40,"id":"82cfc37b-bb11-47bd-968a-637f15c4327a","page_size":[595,841],"block_position":"40-27"}],[{"bbox":[195,94,449,126],"type":"title","angle":0,"index":0,"text":"# Armstrong公理系统","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":41,"id":"01a58eca-0fb2-48d8-ba46-ab4ca08c8109","page_size":[595,841],"block_position":"41-0"},{"bbox":[116,137,273,155],"type":"title","angle":0,"index":1,"text":"# Armstrong公理系统","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":41,"id":"96d56d25-d629-46f2-ada8-c2ab22cf366f","page_size":[595,841],"block_position":"41-1"},{"bbox":[131,156,530,174],"type":"text","angle":0,"index":2,"text":"设有关系模式 R(U,F)，X、Y、Z、 ${ \\boldsymbol { \\mathsf { W } } } \\subseteq { \\boldsymbol { \\mathsf { U } } }$ ，则对 R(U,F)有:","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"id":"b7e1a813-98d0-4e55-8d3a-d4009afe0066","page_size":[595,841],"block_position":"41-2"},{"bbox":[136,176,351,190],"type":"text","angle":0,"index":3,"text":"$\\mathbf { \\hat { \\Pi } } ^ { \\mathbf { \\Pi } }$ A1（自反律）：若YcX，则X $ \\mathsf { Y }$ ；","id":"370a1d5f-8050-4ff5-9ce9-d246b5fcead1","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-3"},{"bbox":[136,192,362,206],"type":"text","angle":0,"index":4,"text":"$\\mathbf { \\hat { \\Pi } } _ { \\infty }$ A2（增广律）：若X $ \\mathsf { Y }$ ，则XZ→YZ;","id":"1f90e129-4465-4a08-9818-e7a1e42ab4c0","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-4"},{"bbox":[136,208,387,222],"type":"text","angle":0,"index":5,"text":"$\\mathbf { \\hat { \\Pi } } ^ { \\mathbf { \\Pi } } \\mathbf { \\hat { \\Pi } } ^ { \\mathbf { \\hat { \\Pi } } }$ A3（传递律）：若X $ \\mathsf { Y }$ $\\Upsilon { } Z$ ，则 $\\pmb { \\mathrm { x } } { } \\pmb { \\mathrm { z } }$","id":"afe91cbf-9421-490c-8758-e05d42854f23","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-5"},{"bbox":[116,226,528,259],"type":"text","angle":0,"index":7,"text":"定理Armstrong公理是正确的。即如果函数依赖F成立，则由F根据Armstrong公理所推导的函数依赖总是成立的。","id":"c33f75f6-5bb3-40d5-9012-c048328fa0a1","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-6"},{"bbox":[116,261,458,280],"type":"text","angle":0,"index":8,"text":"由Armstrong公理系统，可以得到以下三个推论：","id":"1e7dc044-b146-4235-87f1-297306d1257b","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-7"},{"bbox":[136,280,367,295],"type":"text","angle":0,"index":10,"text":"$\\mathbf { \\hat { \\Pi } } _ { \\infty }$ 合成规则：若X $\\displaystyle \\to \\mathsf { Y }$ $\\tt X \\to \\tt Z$ ，则 $\\tt X \\to \\tt Y Z$ ；","id":"9d65d6a8-cf08-4a39-83b7-229ca5a43e18","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-8"},{"bbox":[136,297,364,312],"type":"text","angle":0,"index":11,"text":"$\\mathbf { \\sigma } \\infty$ 86 分解规则：若X $ \\mathsf { Y }$ $\\mathsf { Z } \\subseteq \\mathsf { Y }$ ，则X→Z;","id":"da7e2399-4707-421f-a3dc-8f5307618fff","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-9"},{"bbox":[136,313,394,327],"type":"text","angle":0,"index":12,"text":"$\\mathbf { \\Pi } _ { \\infty } ^ { \\infty }$ 伪传递规则：若X $\\to \\mathsf { Y }$ ${ \\pmb { \\mathsf { W } } } { } { \\pmb { \\mathsf { Z } } }$ ，则XW $ z$","id":"5bfaefb1-b80f-4f1f-a1b0-7038497c6b03","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-10"},{"bbox":[116,330,483,367],"type":"text","angle":0,"index":14,"text":"引理 $\\pmb { \\mathrm { x } } $ A1A2...Ak成立的充分必要条件是X Ai成立2024/6=1,2,..,.k）","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"id":"9577f268-c914-498b-bc67-8c33f4998d0b","page_size":[595,841],"block_position":"41-11"},{"bbox":[516,358,527,366],"type":"text","angle":0,"index":15,"text":"59","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"id":"16293b6f-e1a1-4b82-a335-268aa0c75a8e","page_size":[595,841],"block_position":"41-12"},{"bbox":[86,390,143,403],"type":"title","angle":0,"index":16,"text":"# 最小依赖集","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":41,"id":"bb3e6e94-bb5c-476a-a57e-1e35e3363a60","page_size":[595,841],"block_position":"41-13"},{"bbox":[87,406,161,419],"type":"text","angle":0,"index":17,"text":"1、 右部最小化","id":"966be3ea-ddd8-4b8f-9292-83542c007eba","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-14"},{"bbox":[86,421,354,434],"type":"text","angle":0,"index":18,"text":"2、 除本闭包（如果推出了本身，就不需要这个以来条件）","id":"c4f41195-cdf2-4797-be5d-af5473b51bc4","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-15"},{"bbox":[87,437,161,450],"type":"text","angle":0,"index":19,"text":"3、左部最小化","id":"a7c93d08-79b5-460c-bf90-9d7b51bd551f","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":41,"page_size":[595,841],"block_position":"41-16"},{"bbox":[129,486,257,501],"type":"title","angle":0,"index":21,"text":"# 关系代数与SQL的转化","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":41,"id":"ba36ee95-9ba9-44e6-8a09-ffdb990231ed","page_size":[595,841],"block_position":"41-17"},{"bbox":[106,504,283,616],"index":22,"angle":0,"type":"table_body","img_path":"/","id":"92cde2e5-aecd-4f6d-8ecb-42d5b2192298","color":{"line":"rgba(103, 194, 63, 1)","fill":"rgba(103, 194, 63, 1)"},"table_body":"
名称英文符号说明
选择selectσ类似于 SQL 中的 where
投影projectΠ类似于 SQL 中的 select
并unionU类似于 SQL 中的 union
集合差set-difference-类似于 SQL 中的 Except/Minus
笛卡儿积Cartesian-product×类似于 SQL 中不带 on 条件的 inner join
重命名rewriteρ类似于 SQL 中的 as
集合交intersection∩类似于 SQL 中的 intersect
自然连接natural join⊗类似于 SQL 中的 inner join
","page_idx":41,"page_size":[595,841],"block_position":"41-18"}],[{"bbox":[238,85,330,111],"type":"title","angle":0,"index":0,"text":"# 语法分析","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":42,"id":"c83dc00e-48bf-4f55-8af8-ee9bf1bb6f26","page_size":[595,841],"block_position":"42-0"},{"bbox":[111,118,335,139],"type":"title","angle":0,"index":1,"text":"# “多种等价的关系代数表达式：","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":42,"id":"cf1e0d03-9048-47d8-85a8-b19ab9227e64","page_size":[595,841],"block_position":"42-1"},{"bbox":[112,143,465,165],"type":"text","angle":0,"index":2,"text":"Q1:((te))","id":"6f411299-448c-4855-a4c3-2cb372df971f","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"page_size":[595,841],"block_position":"42-2"},{"bbox":[112,167,419,189],"type":"text","angle":0,"index":3,"text":"Q2: 7 nde=?( student grade))","id":"88719e3d-1a2e-4260-af57-d87a64a9f9c3","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"page_size":[595,841],"block_position":"42-3"},{"bbox":[112,191,413,214],"type":"text","angle":0,"index":4,"text":"Q3: Tsname (StudentOgrac-(grade))","id":"876de825-dc96-45cc-b258-64bc7b83652a","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"page_size":[595,841],"block_position":"42-4"},{"bbox":[87,265,309,279],"type":"text","angle":0,"index":6,"text":"假设有 1000 块 grade 元组，1000 块 student 元组","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"d784dc7b-5dd5-4b8d-b4e2-aed87c7d54cb","page_size":[595,841],"block_position":"42-5"},{"bbox":[89,280,426,337],"type":"text","angle":0,"index":7,"text":"设内存有6块，每个块可装10个Student元组或100个Grade元组。每秒读写20块。假设5块装Student元组，1块装Grade元组。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"9f50bc39-7d62-499a-90ee-7935c0a9af7f","page_size":[595,841],"block_position":"42-6"},{"bbox":[93,342,123,359],"type":"text","angle":0,"index":8,"text":"Q1:","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"8d624ac0-47b3-44a1-9baf-d0c63e076c8c","page_size":[595,841],"block_position":"42-7"},{"bbox":[125,364,424,388],"type":"text","angle":0,"index":9,"text":"2 ( student X grade)sname","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"9b8bc405-2ac7-4bc0-920e-4af61ac13112","page_size":[595,841],"block_position":"42-8"},{"bbox":[94,389,140,405],"type":"text","angle":0,"index":10,"text":"1.×:","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"4cc4eace-5083-4300-896c-c7cc89c0e439","page_size":[595,841],"block_position":"42-9"},{"bbox":[107,411,402,448],"type":"text","angle":0,"index":11,"text":"读 1000/10+ (1000/50)*(10000/100)=2100块[105秒]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"0507af9d-557e-4ca4-b624-a2e44a054619","page_size":[595,841],"block_position":"42-10"},{"bbox":[105,449,369,467],"type":"text","angle":0,"index":12,"text":"写 1000*10000/10 =100000块[50000秒]","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"f9b74331-ce66-4a81-98d5-a193259c7dce","page_size":[595,841],"block_position":"42-11"},{"bbox":[92,470,224,486],"type":"text","angle":0,"index":13,"text":"2．选择：读50000秒","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"8d1ac46c-2bb5-47e0-804a-8629374ebe57","page_size":[595,841],"block_position":"42-12"},{"bbox":[89,491,185,507],"type":"text","angle":0,"index":14,"text":"73．投影：忽略","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"4ec1bd6b-944b-47bc-9453-a35120593150","page_size":[595,841],"block_position":"42-13"},{"bbox":[87,515,320,528],"type":"text","angle":0,"index":15,"text":"1、一共装了 50 个 student 元组、100 个 grade 元组","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"e6af5e8d-b7df-4c13-8b85-73b78ca17a03","page_size":[595,841],"block_position":"42-14"},{"bbox":[88,530,199,544],"type":"text","angle":0,"index":16,"text":"首先从内存中读取数据。","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"5aba94ca-bc93-4753-8359-3ba916d8fe98","page_size":[595,841],"block_position":"42-15"},{"bbox":[88,546,200,559],"type":"text","angle":0,"index":17,"text":"读取 student 表的所有块","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":42,"id":"fcdae01e-15a5-4d78-9329-bb80bcd8fd0c","page_size":[595,841],"block_position":"42-16"}],[{"bbox":[179,121,421,149],"type":"title","angle":0,"index":0,"text":"# 查询优化的一般策略","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"level":1,"page_idx":43,"id":"ddcae268-514d-4757-92ac-0c28e864cb72","page_size":[595,841],"block_position":"43-0"},{"bbox":[99,173,255,195],"type":"text","angle":0,"index":1,"text":"选择尽可能先做","id":"ef1ebe81-d317-4ec8-9072-4eeea08b368d","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"page_size":[595,841],"block_position":"43-1"},{"bbox":[99,201,235,223],"type":"text","angle":0,"index":2,"text":"连接前预处理","id":"1a2b58ad-0612-42fe-a3ce-8810eeb68f4f","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"page_size":[595,841],"block_position":"43-2"},{"bbox":[120,229,186,248],"type":"text","angle":0,"index":4,"text":"6建索引","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"id":"acf962ec-8689-4daf-abc5-8e126660e31c","page_size":[595,841],"block_position":"43-3"},{"bbox":[120,253,171,272],"type":"text","angle":0,"index":5,"text":"排序","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"id":"d737bf53-0888-411e-950b-0f8ee6633226","page_size":[595,841],"block_position":"43-4"},{"bbox":[99,279,254,300],"type":"text","angle":0,"index":6,"text":"选择与投影合并","id":"7ce8c19f-1428-4210-a107-e0a6b64dddc9","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"page_size":[595,841],"block_position":"43-5"},{"bbox":[99,306,332,328],"type":"text","angle":0,"index":7,"text":"投影与其他双目运算合并","id":"2c60b9d1-01ce-4962-9e73-d02aebbed8ca","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"page_size":[595,841],"block_position":"43-6"},{"bbox":[99,335,352,356],"type":"text","angle":0,"index":8,"text":"选择与笛卡儿积合并成连接","id":"806f9512-57d8-42dd-a6ad-4e20c3ab8869","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"page_size":[595,841],"block_position":"43-7"},{"bbox":[99,363,333,384],"type":"text","angle":0,"index":9,"text":"公共子表达式只计算一次","id":"f0f955e9-625b-4f6c-8efd-9a79c87963a7","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"page_size":[595,841],"block_position":"43-8"},{"bbox":[88,406,142,419],"type":"text","angle":0,"index":11,"text":"从下往上写","color":{"line":"rgba(13, 83, 222, 1)","fill":"rgba(13, 83, 222, 1)"},"page_idx":43,"id":"b7d60d56-0b36-4b5f-9b69-28e8c59af107","page_size":[595,841],"block_position":"43-9"}]],"mergeConnections":[{"id":"c836cbbb-4976-42c7-bf30-1abbab8c6af5","blocks":["6-22","7-0"],"type":"merge"}]}