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408, 327 ], "type": "text", "content": "对象间的联系—》实体集间的联系—》属性、关系（表），外码", "score": 1.0 } ] } ] }, { "bbox": [ 86, 328, 309, 341 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 89, 329, 309, 342 ], "spans": [ { "bbox": [ 89, 329, 309, 342 ], "type": "text", "content": "采用ER方法进行数据库概念设计分成三步进行：", "score": 1.0 } ] } ] }, { "bbox": [ 86, 343, 258, 356 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 344, 258, 357 ], "spans": [ { "bbox": [ 89, 344, 258, 357 ], "type": "text", "content": "实体、属性、实体集、联系、域、码", "score": 1.0 } ] } ] }, { "bbox": [ 86, 359, 342, 372 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 358, 344, 374 ], "spans": [ { "bbox": [ 88, 358, 344, 374 ], "type": "text", "content": "联系的类型（阶）：1：1、1：N（或者 N：1）、M：N", "score": 1.0 } ] } ] }, { "bbox": [ 87, 406, 180, 418 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 407, 181, 421 ], "spans": [ { "bbox": [ 88, 407, 181, 421 ], "type": "text", "content": 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341, 497 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 98, 485, 341, 497 ], "spans": [ { "bbox": [ 98, 485, 341, 497 ], "type": "text", "content": "实体类型的合并；冗余属性的消除；冗余联系的消除", "score": 1.0 } ] } ] }, { "bbox": [ 86, 500, 504, 590 ], "type": "list", "angle": 0, "index": 27, "blocks": [ { "bbox": [ 87, 500, 352, 512 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 500, 353, 513 ], "spans": [ { "bbox": [ 88, 500, 353, 513 ], "type": "text", "content": "(1) 二维表格 在关系模型中，一张二维表格对应一个关系。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 515, 436, 528 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 515, 437, 529 ], "spans": [ { "bbox": [ 88, 515, 437, 529 ], "type": "text", "content": "(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。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 531, 383, 543 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 531, 383, 544 ], "spans": [ { "bbox": [ 88, 531, 383, 544 ], "type": "text", "content": "(3) 域 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"index": 28, "lines": [ { "bbox": [ 89, 594, 420, 607 ], "spans": [ { "bbox": [ 89, 594, 420, 607 ], "type": "text", "content": "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）", "score": 1.0 } ] } ] }, { "bbox": [ 99, 616, 276, 629 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 99, 615, 277, 629 ], "spans": [ { "bbox": [ 99, 615, 277, 629 ], "type": "text", "content": "关系中每一个属性值都是不可分解的；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 631, 321, 645 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 100, 631, 322, 645 ], "spans": [ { "bbox": [ 100, 631, 322, 645 ], "type": "text", "content": "关系中不允许出现相同的元组（没有重复元组)；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 648, 265, 661 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 100, 646, 265, 661 ], "spans": [ { "bbox": [ 100, 646, 265, 661 ], "type": "text", "content": "不考虑元组间的顺序，即没有行序；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 663, 339, 676 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 99, 662, 339, 677 ], "spans": [ { "bbox": [ 99, 662, 339, 677 ], "type": "text", "content": "在理论上，属性间的顺序（即列序）也是不存在的；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 678, 411, 691 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 99, 677, 413, 692 ], "spans": [ { "bbox": [ 99, 677, 413, 692 ], "type": "text", "content": "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；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 694, 380, 707 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 101, 694, 380, 707 ], "spans": [ { "bbox": [ 101, 694, 380, 707 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 89, 717, 458, 730 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 91, 717, 459, 732 ], "spans": [ { "bbox": [ 91, 717, 459, 732 ], "type": "text", "content": "(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；", "score": 1.0 } ] } ] }, { "bbox": [ 87, 732, 504, 761 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 90, 732, 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"lines": [ { "bbox": [ 101, 366, 381, 382 ], "spans": [ { "bbox": [ 101, 366, 381, 382 ], "type": "text", "content": "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；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 382, 369, 395 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 102, 383, 370, 396 ], "spans": [ { "bbox": [ 102, 383, 370, 396 ], "type": "text", "content": "两个关系可以是同一个关系模式，表示了属性之间的联系。", "score": 1.0 } ] } ] }, { "bbox": [ 99, 398, 281, 411 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 102, 399, 281, 412 ], "spans": [ { "bbox": [ 102, 399, 281, 412 ], "type": "text", "content": "外码值是否允许空，应视具体情况而定", "score": 1.0 } ] } ] }, { "bbox": [ 86, 421, 508, 465 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 421, 511, 434 ], "spans": [ { "bbox": [ 88, 421, 511, 434 ], "type": "text", "content": "(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，", "score": 1.0 } ] }, { "bbox": [ 89, 438, 505, 450 ], "spans": [ { "bbox": [ 89, 438, 505, 450 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 453, 359, 465 ], "spans": [ { "bbox": [ 89, 453, 359, 465 ], "type": "text", "content": "满足的语义要求。 系统提供定义和检验这类完整性的机制。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 471, 265, 484 ], "type": "title", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 471, 267, 486 ], "spans": [ { "bbox": [ 88, 471, 267, 486 ], "type": "text", "content": "3 数据模型和关系数据模型的基本概念", "score": 1.0 } ] } ] }, { "bbox": [ 87, 487, 180, 499 ], "type": "title", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 487, 180, 501 ], "spans": [ { "bbox": [ 88, 487, 180, 501 ], "type": "text", "content": "3.1 数据模型三要素", "score": 1.0 } ] } ] }, { "bbox": [ 87, 502, 227, 515 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 89, 502, 227, 517 ], "spans": [ { "bbox": [ 89, 502, 227, 517 ], "type": "text", "content": "考核要求：达到“识记”层次", "score": 1.0 } ] } ] }, { "bbox": [ 87, 518, 289, 531 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 89, 518, 290, 532 ], "spans": [ { "bbox": [ 89, 518, 290, 532 ], "type": "text", "content": "知识点：数据结构、数据操作、完整性约束", "score": 1.0 } ] } ] }, { "bbox": [ 88, 534, 250, 547 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 91, 535, 249, 547 ], "spans": [ { "bbox": [ 91, 535, 249, 547 ], "type": "text", "content": "结合下面的关系数据模型进行理解", "score": 1.0 } ] } ] }, { "bbox": [ 87, 565, 201, 577 ], "type": "title", "angle": 0, "index": 18, "lines": [ { "bbox": [ 88, 565, 201, 577 ], "spans": [ { "bbox": [ 88, 565, 201, 577 ], "type": "text", "content": "3.2 二维表格的基本术语", "score": 1.0 } ] } ] }, { "bbox": [ 87, 580, 227, 593 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 89, 580, 227, 595 ], "spans": [ { "bbox": [ 89, 580, 227, 595 ], "type": "text", "content": "考核要求：达到“识记”层次", "score": 1.0 } ] } ] }, { "bbox": [ 87, 596, 227, 608 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 89, 597, 227, 610 ], "spans": [ { "bbox": [ 89, 597, 227, 610 ], "type": "text", "content": "知识点：主要是一些基本概念", "score": 1.0 } ] } ] }, { "bbox": [ 86, 627, 496, 718 ], "type": "list", "angle": 0, "index": 26, "blocks": [ { "bbox": [ 86, 627, 352, 640 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 89, 628, 353, 641 ], "spans": [ { "bbox": [ 89, 628, 353, 641 ], "type": "text", "content": "(1) 二维表格 在关系模型中，一张二维表格对应一个关系。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 643, 436, 655 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 642, 437, 657 ], "spans": [ { "bbox": [ 88, 642, 437, 657 ], "type": "text", "content": "(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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 659, 383, 671 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 659, 384, 672 ], "spans": [ { "bbox": [ 88, 659, 384, 672 ], "type": "text", "content": "(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）", "score": 1.0 } ] } ] }, { "bbox": [ 87, 674, 247, 687 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 674, 248, 688 ], "spans": [ { "bbox": [ 88, 674, 248, 688 ], "type": "text", "content": "(4) 笛卡尔积域上的一种集合运算。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 690, 496, 718 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 89, 690, 498, 703 ], "spans": [ { "bbox": [ 89, 690, 201, 703 ], "type": "text", "content": "(5) 关系：是一个元数为", "score": 1.0 }, { "bbox": [ 201, 691, 236, 703 ], "type": "inline_equation", "content": "\\mathsf { K } ( \\mathsf { K } > = 1 )", "score": 0.85 }, { "bbox": [ 236, 690, 498, 703 ], "type": "text", "content": "的元组的集合。 一张二维表格对应一个关系。表中的一", "score": 1.0 } ] }, { "bbox": [ 89, 704, 358, 719 ], "spans": [ { "bbox": [ 89, 704, 358, 719 ], "type": "text", "content": "行称为关系的一个元组；表中的一列称为关系的一个属性。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 86, 721, 419, 734 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 89, 721, 420, 735 ], "spans": [ { "bbox": [ 89, 721, 420, 735 ], "type": "text", "content": "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）", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 4 }, { "para_blocks": [ { "bbox": [ 101, 89, 278, 104 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 102, 89, 279, 105 ], "spans": [ { "bbox": [ 102, 89, 279, 105 ], "type": "text", "content": "关系中每一个属性值都是不可分解的；", "score": 1.0 } ] } ] }, { "bbox": [ 101, 105, 323, 119 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 102, 104, 324, 121 ], "spans": [ { "bbox": [ 102, 104, 324, 121 ], "type": "text", "content": "关系中不允许出现相同的元组（没有重复元组)；", "score": 1.0 } ] } ] }, { "bbox": [ 101, 121, 268, 134 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 102, 121, 268, 135 ], "spans": [ { "bbox": [ 102, 121, 268, 135 ], "type": "text", "content": "不考虑元组间的顺序，即没有行序；", "score": 1.0 } ] } ] }, { "bbox": [ 101, 137, 341, 150 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 101, 136, 342, 151 ], "spans": [ { "bbox": [ 101, 136, 342, 151 ], "type": "text", "content": "在理论上，属性间的顺序（即列序）也是不存在的；", "score": 1.0 } ] } ] }, { "bbox": [ 101, 152, 414, 166 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 102, 151, 415, 167 ], "spans": [ { "bbox": [ 102, 151, 415, 167 ], "type": "text", "content": "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；", "score": 1.0 } ] } ] }, { "bbox": [ 101, 168, 382, 181 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 102, 168, 383, 182 ], "spans": [ { "bbox": [ 102, 168, 383, 182 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 191, 498, 282 ], "type": "list", "angle": 0, "index": 9, "blocks": [ { "bbox": [ 89, 191, 459, 205 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 91, 191, 459, 206 ], "spans": [ { "bbox": [ 91, 191, 459, 206 ], "type": "text", "content": "(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；", "score": 1.0 } ] } ] }, { "bbox": [ 86, 206, 498, 251 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 90, 206, 498, 221 ], "spans": [ { "bbox": [ 90, 206, 498, 221 ], "type": "text", "content": "(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", "score": 1.0 } ] }, { "bbox": [ 89, 222, 497, 236 ], "spans": [ { "bbox": [ 89, 222, 497, 236 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 238, 128, 253 ], "spans": [ { "bbox": [ 88, 238, 128, 253 ], "type": "text", "content": "候选码。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 253, 498, 282 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 90, 253, 499, 268 ], "spans": [ { "bbox": [ 90, 253, 499, 268 ], "type": "text", "content": "(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", "score": 1.0 } ] }, { "bbox": [ 88, 269, 232, 283 ], "spans": [ { "bbox": [ 88, 269, 232, 283 ], "type": "text", "content": "码，则选择其中一个作为主码。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 86, 285, 452, 298 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 285, 452, 299 ], "spans": [ { "bbox": [ 88, 285, 452, 299 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 93, 306, 499, 384 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 95, 306, 499, 322 ], "spans": [ { "bbox": [ 95, 306, 499, 322 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 96, 323, 492, 336 ], "spans": [ { "bbox": [ 96, 323, 492, 336 ], "type": "text", "content": "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）", "score": 1.0 } ] }, { "bbox": [ 96, 339, 498, 352 ], "spans": [ { "bbox": [ 96, 339, 498, 352 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 96, 354, 497, 367 ], "spans": [ { "bbox": [ 96, 354, 497, 367 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 96, 370, 345, 383 ], "spans": [ { "bbox": [ 96, 370, 345, 383 ], "type": "text", "content": "两个或两个以上候选码，用户就选其中之一作为主码。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 392, 201, 406 ], "type": "title", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 392, 201, 407 ], "spans": [ { "bbox": [ 88, 392, 201, 407 ], "type": "text", "content": "3.3 关系模型的形式定义", "score": 1.0 } ] } ] }, { "bbox": [ 87, 408, 227, 422 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 89, 408, 227, 423 ], "spans": [ { "bbox": [ 89, 408, 227, 423 ], "type": "text", "content": "考核要求：达到“识记”层次", "score": 1.0 } ] } ] }, { "bbox": [ 87, 424, 227, 438 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 424, 227, 439 ], "spans": [ { "bbox": [ 89, 424, 227, 439 ], "type": "text", "content": "知识点：三个组成部分的了解", "score": 1.0 } ] } ] }, { "bbox": [ 86, 455, 394, 469 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 89, 456, 394, 469 ], "spans": [ { "bbox": [ 89, 456, 394, 469 ], "type": "text", "content": "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", "score": 1.0 } ] } ] }, { "bbox": [ 87, 470, 232, 484 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 89, 470, 233, 485 ], "spans": [ { "bbox": [ 89, 470, 233, 485 ], "type": "text", "content": "关系模型的的数据结构是关系；", "score": 1.0 } ] } ] }, { "bbox": [ 86, 486, 498, 516 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 89, 486, 498, 500 ], "spans": [ { "bbox": [ 89, 486, 327, 500 ], "type": "text", "content": "关系模型提供一组完备的高级关系运算（关系代数", "score": 1.0 }, { "bbox": [ 327, 488, 334, 498 ], "type": "inline_equation", "content": "^ +", "score": 0.74 }, { "bbox": [ 335, 486, 498, 500 ], "type": "text", "content": "关系演算），支持数据库的各种操", "score": 1.0 } ] }, { "bbox": [ 87, 501, 109, 518 ], "spans": [ { "bbox": [ 87, 501, 109, 518 ], "type": "text", "content": "作；", "score": 1.0 } ] } ] }, { "bbox": [ 87, 518, 230, 530 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 518, 230, 531 ], "spans": [ { "bbox": [ 89, 518, 230, 531 ], "type": "text", "content": "关系模型包括三类完整性规则。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 549, 232, 562 ], "type": "title", "angle": 0, "index": 19, "lines": [ { "bbox": [ 89, 550, 232, 563 ], "spans": [ { "bbox": [ 89, 550, 232, 563 ], "type": "text", "content": "3.4 关系模型的三类完整性规则", "score": 1.0 } ] } ] }, { "bbox": [ 86, 564, 430, 577 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 88, 563, 431, 579 ], "spans": [ { "bbox": [ 88, 563, 431, 579 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 580, 237, 592 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 89, 580, 238, 593 ], "spans": [ { "bbox": [ 89, 580, 238, 593 ], "type": "text", "content": "知识点：三类完整性规则的理解", "score": 1.0 } ] } ] }, { "bbox": [ 86, 611, 498, 687 ], "type": "list", "angle": 0, "index": 24, "blocks": [ { "bbox": [ 86, 611, 498, 655 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 89, 612, 492, 624 ], "spans": [ { "bbox": [ 89, 612, 492, 624 ], "type": "text", "content": "(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，", "score": 1.0 } ] }, { "bbox": [ 88, 627, 498, 640 ], "spans": [ { "bbox": [ 88, 627, 498, 640 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 642, 114, 657 ], "spans": [ { "bbox": [ 88, 642, 114, 657 ], "type": "text", "content": "主键", "score": 1.0 } ] } ] }, { "bbox": [ 87, 657, 492, 687 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 658, 492, 671 ], "spans": [ { "bbox": [ 88, 658, 492, 671 ], "type": "text", "content": "(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。", "score": 1.0 } ] }, { "bbox": [ 95, 673, 189, 687 ], "spans": [ { "bbox": [ 95, 673, 189, 687 ], "type": "text", "content": "（对关系外码的约束）", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 101, 696, 498, 726 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 104, 697, 497, 711 ], "spans": [ { "bbox": [ 104, 697, 497, 711 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 104, 712, 399, 725 ], "spans": [ { "bbox": [ 104, 712, 399, 725 ], "type": "text", "content": "一个关系（比如选课关系SC）中，此时称Sno是关系SC的外码。", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 5 }, { "para_blocks": [ { "bbox": [ 102, 105, 151, 118 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 103, 106, 154, 120 ], "spans": [ { "bbox": [ 103, 106, 154, 120 ], "type": "text", "content": "注意事项：", "score": 1.0 } ] } ] }, { "bbox": [ 102, 121, 382, 135 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 104, 121, 383, 136 ], "spans": [ { "bbox": [ 104, 121, 383, 136 ], "type": "text", "content": "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；", "score": 1.0 } ] } ] }, { "bbox": [ 102, 137, 371, 150 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 104, 137, 372, 151 ], "spans": [ { "bbox": [ 104, 137, 372, 151 ], "type": "text", "content": "两个关系可以是同一个关系模式，表示了属性之间的联系。", "score": 1.0 } ] } ] }, { "bbox": [ 102, 153, 284, 166 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 104, 153, 283, 166 ], "spans": [ { "bbox": [ 104, 153, 283, 166 ], "type": "text", "content": "外码值是否允许空，应视具体情况而定", "score": 1.0 } ] } ] }, { "bbox": [ 102, 183, 214, 195 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 102, 183, 215, 195 ], "spans": [ { "bbox": [ 102, 183, 215, 195 ], "type": "text", "content": "假设数据库有如下关系：", "score": 1.0 } ] } ] }, { "bbox": [ 102, 199, 269, 211 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 102, 197, 270, 213 ], "spans": [ { "bbox": [ 102, 197, 270, 213 ], "type": "text", "content": "学生关系 S (S#、SNAME、AGE、SEX)", "score": 1.0 } ] } ] }, { "bbox": [ 102, 214, 273, 227 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 101, 212, 274, 228 ], "spans": [ { "bbox": [ 101, 212, 274, 228 ], "type": "text", "content": "课程关系 C（C#、CNAME、TEACHER）", "score": 1.0 } ] } ] }, { "bbox": [ 102, 230, 246, 243 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 102, 228, 246, 243 ], "spans": [ { "bbox": [ 102, 228, 246, 243 ], "type": "text", "content": "学习关系 SC（S#、C#、GRADE）", "score": 1.0 } ] } ] }, { "bbox": [ 102, 245, 126, 258 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 100, 242, 128, 259 ], "spans": [ { "bbox": [ 100, 242, 128, 259 ], "type": "text", "content": "那么", "score": 1.0 } ] } ] }, { "bbox": [ 102, 260, 424, 290 ], "type": "list", "angle": 0, "index": 11, "blocks": [ { "bbox": [ 102, 260, 422, 274 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 101, 259, 423, 275 ], "spans": [ { "bbox": [ 101, 259, 423, 275 ], "type": "text", "content": "(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）", "score": 1.0 } ] } ] }, { "bbox": [ 102, 276, 424, 290 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 101, 275, 425, 290 ], "spans": [ { "bbox": [ 101, 275, 425, 290 ], "type": "text", "content": "(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）", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 102, 292, 155, 304 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 102, 290, 157, 305 ], "spans": [ { "bbox": [ 102, 290, 157, 305 ], "type": "text", "content": "关系SC中：", "score": 1.0 } ] } ] }, { "bbox": [ 110, 307, 457, 321 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 108, 306, 458, 322 ], "spans": [ { "bbox": [ 108, 306, 458, 322 ], "type": "text", "content": "（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）", "score": 1.0 } ] } ] }, { "bbox": [ 102, 323, 474, 352 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 101, 322, 476, 337 ], "spans": [ { "bbox": [ 101, 322, 476, 337 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 99, 337, 122, 354 ], "spans": [ { "bbox": [ 99, 337, 122, 354 ], "type": "text", "content": "则）", "score": 1.0 } ] } ] }, 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469 ], "type": "title", "angle": 0, "index": 17, "lines": [ { "bbox": [ 89, 455, 359, 470 ], "spans": [ { "bbox": [ 89, 455, 359, 470 ], "type": "text", "content": "4 概念模型向关系数据模型的转化（即 ER 图转化为表结构）", "score": 1.0 } ] } ] }, { "bbox": [ 86, 470, 248, 484 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 470, 248, 484 ], "spans": [ { "bbox": [ 89, 470, 248, 484 ], "type": "text", "content": "考核要求：达到“熟练掌握”层次", "score": 1.0 } ] } ] }, { "bbox": [ 86, 486, 206, 499 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 89, 486, 207, 500 ], "spans": [ { "bbox": [ 89, 486, 207, 500 ], "type": "text", "content": "知识点：转换的实际操作", "score": 1.0 } ] } ] }, { "bbox": [ 86, 502, 257, 515 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 89, 502, 257, 516 ], "spans": [ { "bbox": [ 89, 502, 257, 516 ], "type": "text", "content": "ER模型转换关系数据库的 一般规则：", "score": 1.0 } ] } ] }, { "bbox": [ 99, 518, 455, 546 ], "type": "list", "angle": 0, "index": 23, "blocks": [ { "bbox": [ 99, 518, 455, 531 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 102, 518, 456, 531 ], "spans": [ { "bbox": [ 102, 518, 456, 531 ], "type": "text", "content": "（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。", "score": 1.0 } ] } ] }, { "bbox": [ 101, 533, 340, 546 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 102, 533, 341, 548 ], "spans": [ { "bbox": [ 102, 533, 341, 548 ], "type": "text", "content": "（2） 对于二元联系，按各种情况处理，如下面所示。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "type": "table", "bbox": [ 89, 548, 502, 755 ], "blocks": [ { "bbox": [ 89, 548, 502, 755 ], "lines": [ { "bbox": [ 89, 548, 502, 755 ], "spans": [ { "bbox": [ 89, 548, 502, 755 ], "type": "table", "html": "
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
", "image_path": "0fa0fc4deb0a98640f4b7c3fb29ebbe7162f736d545ee2543f70778170cd28d9.jpg" } ] } ], "index": 24, "angle": 0, "type": "table_body" } ], "index": 24 } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 6 }, { "para_blocks": [ { "type": "table", "bbox": [ 89, 79, 505, 438 ], "blocks": [ { "bbox": [ 89, 79, 505, 438 ], "lines": [], "index": 0, "angle": 0, "type": "table_body", "lines_deleted": true } ], "index": 0 }, { "bbox": [ 86, 458, 505, 502 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 94, 460, 505, 470 ], "spans": [ { "bbox": [ 94, 460, 505, 470 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 474, 505, 486 ], "spans": [ { "bbox": [ 89, 474, 505, 486 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 488, 126, 503 ], "spans": [ { "bbox": [ 88, 488, 126, 503 ], "type": "text", "content": "称\"列\"。", "score": 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"content": "(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", "score": 1.0 } ] }, { "bbox": [ 89, 582, 252, 595 ], "spans": [ { "bbox": [ 89, 582, 252, 595 ], "type": "text", "content": "基本表或其他视图构成的表的定义。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 598, 499, 627 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 93, 598, 499, 612 ], "spans": [ { "bbox": [ 93, 598, 499, 612 ], "type": "text", "content": "(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。", "score": 1.0 } ] }, { "bbox": [ 88, 613, 210, 627 ], "spans": [ { "bbox": [ 88, 613, 210, 627 ], "type": "text", "content": "存储文件与物理文件对应。", "score": 1.0 } ] } ] }, { "bbox": [ 91, 629, 362, 643 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 93, 629, 363, 644 ], "spans": [ { "bbox": [ 93, 629, 363, 644 ], "type": "text", "content": "(5)用户可以用 SQL 语句对表进行操作，包括视图和基本表。", "score": 1.0 } ] } ] }, { "bbox": [ 92, 645, 329, 659 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 93, 645, 329, 660 ], "spans": [ { 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"bbox": [ 86, 624, 202, 637 ], "type": "title", "angle": 0, "index": 32, "lines": [ { "bbox": [ 88, 624, 204, 639 ], "spans": [ { "bbox": [ 88, 624, 204, 639 ], "type": "text", "content": "FROM 基本表或视图序列", "score": 1.0 } ] } ] }, { "bbox": [ 87, 640, 177, 652 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 88, 640, 177, 654 ], "spans": [ { "bbox": [ 88, 640, 177, 654 ], "type": "text", "content": "WHERE 条件表达式", "score": 1.0 } ] } ] }, { "bbox": [ 86, 655, 290, 668 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 88, 656, 292, 669 ], "spans": [ { "bbox": [ 88, 656, 292, 669 ], "type": "text", "content": "Notice:掌握条件表达式中各种运算符的应用.", "score": 1.0 } ] } ] }, { "bbox": [ 99, 678, 268, 692 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 98, 677, 269, 692 ], "spans": [ { "bbox": [ 98, 677, 174, 692 ], "type": "text", "content": "算术比较运算符", "score": 1.0 }, { "bbox": [ 175, 680, 182, 690 ], "type": "inline_equation", "content": "\\dot { } = \\mathbf { \\nabla }", "score": 0.69 }, { "bbox": [ 182, 677, 189, 692 ], "type": "text", "content": "，", "score": 1.0 }, { "bbox": [ 190, 679, 218, 692 ], "type": "inline_equation", "content": "> , < , < >", "score": 0.77 }, { "bbox": [ 218, 677, 229, 692 ], "type": "text", "content": "或!", "score": 1.0 }, { "bbox": [ 229, 679, 264, 692 ], "type": "inline_equation", "content": "! = , < = , > =", "score": 0.87 }, { "bbox": [ 264, 677, 269, 692 ], "type": "text", "content": "；", "score": 1.0 } ] } ] }, { "bbox": [ 100, 694, 233, 707 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 99, 692, 235, 708 ], "spans": [ { "bbox": [ 99, 692, 235, 708 ], "type": "text", "content": "逻辑运算符AND、OR、NOT；", "score": 1.0 } ] } ] }, { "bbox": [ 99, 710, 405, 723 ], "type": "text", "angle": 0, "index": 37, "lines": [ { "bbox": [ 98, 708, 406, 724 ], "spans": [ { "bbox": [ 98, 708, 406, 724 ], "type": "text", "content": "集合成员资格运算符：IN，NOT IN；like， not like；between and ；", "score": 1.0 } ] } ] }, { "bbox": [ 100, 725, 267, 738 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 99, 724, 268, 740 ], "spans": [ { "bbox": [ 99, 724, 268, 740 ], "type": "text", "content": "谓词:EXISTS(存在量词)，NOT EXISTS；", "score": 1.0 } ] } ] }, { "bbox": [ 100, 740, 222, 754 ], "type": "text", "angle": 0, "index": 39, "lines": [ { "bbox": [ 99, 740, 223, 754 ], "spans": [ { "bbox": [ 99, 740, 223, 754 ], "type": "text", "content": "聚合函数：（在下面介绍）", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 8 }, { "para_blocks": [ { "bbox": [ 87, 79, 199, 91 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 79, 200, 92 ], "spans": [ { "bbox": [ 88, 79, 200, 92 ], "type": "text", "content": "(2) SELECT 句型使用实例", "score": 1.0 } ] } ] }, { "bbox": [ 86, 95, 294, 107 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 89, 95, 294, 108 ], "spans": [ { "bbox": [ 89, 95, 294, 108 ], "type": "text", "content": "本节内容需要多看例题，多作习题进行掌握。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 110, 339, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 110, 341, 125 ], "spans": [ { "bbox": [ 88, 110, 341, 125 ], "type": "text", "content": "Notice:嵌套的 SELECT 语句的用法 ，体会结构化的含义。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 126, 144, 137 ], "type": "title", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 126, 145, 139 ], "spans": [ { "bbox": [ 88, 126, 145, 139 ], "type": "text", "content": "(3)聚合函数", "score": 1.0 } ] } ] }, { "bbox": [ 87, 141, 189, 153 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 140, 189, 155 ], "spans": [ { "bbox": [ 88, 140, 189, 155 ], "type": "text", "content": "注意各个函数的含义：", "score": 1.0 } ] } ] }, { "type": "table", "bbox": [ 86, 154, 334, 380 ], "blocks": [ { "bbox": [ 86, 154, 334, 380 ], "lines": [ { "bbox": [ 86, 154, 334, 380 ], "spans": [ { "bbox": [ 86, 154, 334, 380 ], "type": "table", "html": "
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
", "image_path": "98a382000ac801dd9bb89b7433d3aedac021c2567a0da305fc806bc0e28c5dbe.jpg" } ] } ], "index": 5, "angle": 0, "type": "table_body" } ], "index": 5 }, { "bbox": [ 86, 383, 474, 396 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 88, 383, 477, 398 ], "spans": [ { "bbox": [ 88, 383, 477, 398 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 398, 202, 412 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 89, 399, 202, 413 ], "spans": [ { "bbox": [ 89, 399, 202, 413 ], "type": "text", "content": "SELECT 列名表(逗号隔开)", "score": 1.0 } ] } ] }, { "bbox": [ 87, 414, 202, 427 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 88, 414, 204, 428 ], "spans": [ { "bbox": [ 88, 414, 204, 428 ], "type": "text", "content": "FROM 基本表或视图序列", "score": 1.0 } ] } ] }, { "bbox": [ 87, 430, 244, 443 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 430, 245, 444 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492, 198, 506 ], "type": "text", "content": "(1)SELECT 子句中的规定", "score": 1.0 } ] } ] }, { "bbox": [ 104, 507, 453, 536 ], "type": "list", "angle": 0, "index": 16, "blocks": [ { "bbox": [ 104, 507, 453, 520 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 104, 506, 455, 523 ], "spans": [ { "bbox": [ 104, 506, 455, 523 ], "type": "text", "content": " 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", "score": 1.0 } ] } ] }, { "bbox": [ 104, 523, 431, 536 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 104, 523, 432, 538 ], "spans": [ { "bbox": [ 104, 523, 232, 538 ], "type": "text", "content": " SELECT 子句中允许出现", "score": 1.0 }, { "bbox": [ 232, 524, 261, 537 ], "type": "inline_equation", "content": "{ + , ^ { - } , ^ { * } , / } ,", "score": 0.88 }, { "bbox": [ 261, 523, 432, 538 ], "type": "text", "content": ",以及列名、常数、函数的算术表达式", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 87, 539, 230, 552 ], "type": "title", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 539, 230, 552 ], "spans": [ { "bbox": [ 88, 539, 230, 552 ], "type": "text", "content": "(2) 条件表达式的算术比较操作", "score": 1.0 } ] } ] }, { "bbox": [ 104, 555, 397, 567 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 104, 554, 398, 569 ], "spans": [ { "bbox": [ 104, 554, 398, 569 ], "type": "text", "content": " WHERE 子句中可以用 BETWEEN...AND...来限定一个值的范围", "score": 1.0 } ] } ] }, { "bbox": [ 88, 570, 207, 582 ], "type": "title", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 570, 207, 584 ], "spans": [ { "bbox": [ 88, 570, 207, 584 ], "type": "text", "content": "(3)列和基本表的改名操作", "score": 1.0 } ] } ] }, { "bbox": [ 104, 586, 406, 598 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 105, 586, 406, 600 ], "spans": [ { "bbox": [ 105, 586, 406, 600 ], "type": "text", "content": " 同一个基本表在 SELECT语句中多次引用时可用AS来增加别名", "score": 1.0 } ] } ] }, { "bbox": [ 88, 601, 186, 614 ], "type": "title", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 601, 186, 615 ], "spans": [ { "bbox": [ 88, 601, 186, 615 ], "type": "text", "content": "(4)字符串的匹配操作", "score": 1.0 } ] } ] }, { "bbox": [ 104, 617, 406, 630 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 104, 616, 408, 632 ], "spans": [ { "bbox": [ 104, 616, 408, 632 ], "type": "text", "content": " WHERE 子句中字符串匹配用 LIKE 和两个通配符，%和下划线_.", "score": 1.0 } ] } ] }, { "bbox": [ 87, 648, 207, 661 ], "type": "title", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 648, 207, 662 ], "spans": [ { "bbox": [ 88, 648, 207, 662 ], "type": "text", "content": "(5)集合的并、交、差操作", "score": 1.0 } ] } ] }, { "bbox": [ 104, 664, 504, 692 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 107, 662, 506, 678 ], "spans": [ { "bbox": [ 107, 662, 506, 678 ], "type": "text", "content": " 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", "score": 1.0 } ] }, { "bbox": [ 130, 677, 170, 694 ], "spans": [ { "bbox": [ 130, 677, 170, 694 ], "type": "text", "content": "（Except）", "score": 1.0 } ] } ] }, { "bbox": [ 88, 695, 175, 708 ], "type": "title", "angle": 0, "index": 25, "lines": [ { "bbox": [ 88, 695, 176, 708 ], "spans": [ { "bbox": [ 88, 695, 176, 708 ], "type": "text", "content": "(6)空值的比较操作", "score": 1.0 } ] } ] }, { "bbox": [ 104, 710, 352, 724 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 122, 709, 353, 724 ], "spans": [ { "bbox": [ 122, 709, 218, 724 ], "type": "text", "content": "查询空值操作不是用", "score": 1.0 }, { "bbox": [ 219, 712, 227, 722 ], "type": "inline_equation", "content": "= \"", "score": 0.55 }, { "bbox": [ 227, 709, 353, 724 ], "type": "text", "content": "null',而是用 IS NULL 来测试。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 726, 175, 739 ], "type": "title", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 726, 176, 739 ], "spans": [ { "bbox": [ 88, 726, 176, 739 ], "type": "text", "content": "(7)集合的比较操作", "score": 1.0 } ] } ] }, { "bbox": [ 105, 742, 267, 755 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 105, 740, 268, 756 ], "spans": [ { "bbox": [ 105, 740, 268, 756 ], "type": "text", "content": " 集合成员资格比较用 IN/NOT IN", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 9 }, { "para_blocks": [ { "bbox": [ 104, 79, 431, 91 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 105, 77, 432, 94 ], "spans": [ { "bbox": [ 105, 77, 432, 94 ], "type": "text", "content": " 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）", "score": 1.0 } ] } ] }, { "bbox": [ 88, 95, 167, 107 ], "type": "title", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 95, 167, 108 ], "spans": [ { "bbox": [ 88, 95, 167, 108 ], "type": "text", "content": "(8) 导出表的使用", "score": 1.0 } ] } ] }, { "bbox": [ 104, 110, 438, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 106, 110, 440, 124 ], "spans": [ { "bbox": [ 106, 110, 440, 124 ], "type": "text", "content": " 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。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 126, 189, 138 ], "type": "title", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 126, 189, 138 ], "spans": [ { "bbox": [ 88, 126, 189, 138 ], "type": "text", "content": "(9) 基本表的连接操作", "score": 1.0 } ] } ] }, { "bbox": [ 88, 141, 504, 200 ], "type": "list", "angle": 0, "index": 6, "blocks": [ { "bbox": [ 104, 141, 317, 154 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 123, 141, 317, 156 ], "spans": [ { "bbox": [ 123, 141, 317, 156 ], "type": "text", "content": "等值连接操作是用 [INNER] JOIN 来实现的。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 157, 504, 200 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 124, 156, 487, 172 ], "spans": [ { "bbox": [ 124, 156, 487, 172 ], "type": "text", "content": "外连接：左外连接 LEFT [OUTER] JOIN 、RIGHT [OUTER] JOIN、FULL [OUTER] JOIN", "score": 1.0 } ] }, { "bbox": [ 89, 173, 505, 186 ], "spans": [ { "bbox": [ 89, 173, 505, 186 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 86, 187, 107, 203 ], "spans": [ { "bbox": [ 86, 187, 107, 203 ], "type": "text", "content": "接。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 88, 203, 189, 216 ], "type": "title", "angle": 0, "index": 7, "lines": [ { "bbox": [ 89, 204, 189, 217 ], "spans": [ { "bbox": [ 89, 204, 189, 217 ], "type": "text", "content": "数据插入方式有两种：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 219, 167, 232 ], "type": "title", "angle": 0, "index": 8, "lines": [ { "bbox": [ 88, 220, 167, 232 ], "spans": [ { "bbox": [ 88, 220, 167, 232 ], "type": "text", "content": "(1) 元组值的插入", "score": 1.0 } ] } ] }, { "bbox": [ 88, 235, 226, 248 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 235, 226, 248 ], "spans": [ { "bbox": [ 88, 235, 226, 248 ], "type": "text", "content": "INSERT INTO 基本表名(列名表)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 251, 155, 263 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 250, 155, 264 ], "spans": [ { "bbox": [ 88, 250, 155, 264 ], "type": "text", "content": "values(元组值)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 266, 177, 279 ], "type": "title", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 266, 178, 280 ], "spans": [ { "bbox": [ 88, 266, 178, 280 ], "type": "text", "content": "(2) 查询结果的插入", "score": 1.0 } ] } ] }, { "bbox": [ 88, 281, 226, 294 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 281, 226, 295 ], "spans": [ { "bbox": [ 88, 281, 226, 295 ], "type": "text", "content": "INSERT INTO 基本表名(列名表)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 297, 164, 309 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 296, 166, 312 ], "spans": [ { "bbox": [ 88, 296, 166, 312 ], "type": "text", "content": "SELECT 查询语句", "score": 1.0 } ] } ] }, { "bbox": [ 88, 312, 229, 325 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 313, 229, 326 ], "spans": [ { "bbox": [ 88, 313, 229, 326 ], "type": "text", "content": "WHERE子句中使用下列关键字", "score": 1.0 } ] } ] }, { "bbox": [ 88, 328, 294, 341 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 328, 294, 343 ], "spans": [ { "bbox": [ 88, 328, 294, 343 ], "type": "text", "content": "除了比较符，可以在 WHERE 子句中使用下列", "score": 1.0 } ] } ] }, { "bbox": [ 88, 343, 121, 356 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 343, 123, 359 ], "spans": [ { "bbox": [ 88, 343, 123, 359 ], "type": "text", "content": "关键字", "score": 1.0 } ] } ] }, { "bbox": [ 88, 359, 121, 372 ], "type": "title", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 359, 123, 375 ], "spans": [ { "bbox": [ 88, 359, 123, 375 ], "type": "text", "content": "关键字", "score": 1.0 } ] } ] }, { "bbox": [ 88, 375, 111, 387 ], "type": "title", "angle": 0, "index": 18, "lines": [ { "bbox": [ 86, 374, 114, 392 ], "spans": [ { "bbox": [ 86, 374, 114, 392 ], "type": "text", "content": "含义", "score": 1.0 } ] } ] }, { "bbox": [ 88, 391, 99, 401 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 391, 101, 406 ], "spans": [ { "bbox": [ 88, 391, 101, 406 ], "type": "text", "content": "IN", "score": 1.0 } ] } ] }, { "bbox": [ 88, 406, 215, 418 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 89, 407, 215, 419 ], "spans": [ { "bbox": [ 89, 407, 215, 419 ], "type": "text", "content": "判断值是否在所给的范围内", "score": 1.0 } ] } ] }, { "bbox": [ 88, 422, 120, 432 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 422, 122, 435 ], "spans": [ { "bbox": [ 88, 422, 122, 435 ], "type": "text", "content": "NOT IN", "score": 1.0 } ] } ] }, { "bbox": [ 88, 437, 226, 450 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 89, 439, 226, 450 ], "spans": [ { "bbox": [ 89, 439, 226, 450 ], "type": "text", "content": "判断值是否不在所给的范围内", "score": 1.0 } ] } ] }, { "bbox": [ 88, 454, 108, 464 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 87, 454, 109, 466 ], "spans": [ { "bbox": [ 87, 454, 109, 466 ], "type": "text", "content": "LIKE", "score": 1.0 } ] } ] }, { "bbox": [ 88, 468, 237, 481 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 89, 470, 237, 481 ], "spans": [ { "bbox": [ 89, 470, 237, 481 ], "type": "text", "content": "判断值是否与一个给定的值相似", "score": 1.0 } ] } ] }, { "bbox": [ 88, 485, 129, 495 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 87, 485, 130, 497 ], "spans": [ { "bbox": [ 87, 485, 130, 497 ], "type": "text", "content": "NOT LIKE", "score": 1.0 } ] } ] }, { "bbox": [ 88, 500, 247, 513 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 89, 501, 248, 513 ], "spans": [ { "bbox": [ 89, 501, 248, 513 ], "type": "text", "content": "判断值是否与一个给定的值不相似", "score": 1.0 } ] } ] }, { "bbox": [ 88, 516, 122, 526 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 515, 124, 530 ], "spans": [ { "bbox": [ 88, 515, 124, 530 ], "type": "text", "content": "IS NULL", "score": 1.0 } ] } ] }, { "bbox": [ 88, 531, 163, 543 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 88, 531, 164, 544 ], "spans": [ { "bbox": [ 88, 531, 164, 544 ], "type": "text", "content": "判断值是否为空", "score": 1.0 } ] } ] }, { "bbox": [ 88, 547, 143, 557 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 88, 548, 144, 560 ], "spans": [ { "bbox": [ 88, 548, 144, 560 ], "type": "text", "content": "IS NOT NULL", "score": 1.0 } ] } ] }, { "bbox": [ 88, 562, 174, 574 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 89, 563, 174, 575 ], "spans": [ { "bbox": [ 89, 563, 174, 575 ], "type": "text", "content": "判断值是否不为空", "score": 1.0 } ] } ] }, { "bbox": [ 88, 578, 110, 588 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 87, 577, 111, 592 ], "spans": [ { "bbox": [ 87, 577, 111, 592 ], "type": "text", "content": "AND", "score": 1.0 } ] } ] }, { "bbox": [ 88, 593, 249, 605 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 88, 593, 251, 607 ], "spans": [ { "bbox": [ 88, 593, 251, 607 ], "type": "text", "content": "判断是否满足AND两边所给的条件", "score": 1.0 } ] } ] }, { "bbox": [ 88, 609, 102, 619 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 88, 609, 105, 622 ], "spans": [ { "bbox": [ 88, 609, 105, 622 ], "type": "text", "content": "OR", "score": 1.0 } ] } ] }, { "bbox": [ 88, 624, 285, 637 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 88, 624, 286, 638 ], "spans": [ { "bbox": [ 88, 624, 286, 638 ], "type": "text", "content": "判断是否满足OR 两边所给的条件中的一个", "score": 1.0 } ] } ] }, { "bbox": [ 88, 640, 158, 650 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 89, 641, 160, 652 ], "spans": [ { "bbox": [ 89, 641, 160, 652 ], "type": "text", "content": "BETWEEN…AND", "score": 1.0 } ] } ] }, { "bbox": [ 88, 655, 215, 668 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 89, 656, 215, 668 ], "spans": [ { "bbox": [ 89, 656, 215, 668 ], "type": "text", "content": "判断值是否在所给的值之间", "score": 1.0 } ] } ] }, { "bbox": [ 88, 671, 180, 682 ], "type": "text", "angle": 0, "index": 37, "lines": [ { "bbox": [ 88, 673, 180, 684 ], "spans": [ { "bbox": [ 88, 673, 180, 684 ], "type": "text", "content": "NOT BETWEEN…AND", "score": 1.0 } ] } ] }, { "bbox": [ 88, 687, 226, 699 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 89, 687, 226, 700 ], "spans": [ { "bbox": [ 89, 687, 226, 700 ], "type": "text", "content": "判断值是否不在所给的值之间", "score": 1.0 } ] } ] }, { "bbox": [ 88, 703, 305, 714 ], "type": "text", "angle": 0, "index": 39, "lines": [ { "bbox": [ 88, 702, 307, 717 ], "spans": [ { "bbox": [ 88, 702, 307, 717 ], "type": "text", "content": "使用 LIKE 运算符可以完成对字符串的模糊匹配。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 719, 96, 729 ], "type": "text", "angle": 0, "index": 40, "lines": [ { "bbox": [ 88, 721, 96, 730 ], "spans": [ { "bbox": [ 88, 721, 96, 730 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 734, 136, 745 ], "type": "text", "angle": 0, "index": 41, "lines": [ { "bbox": [ 88, 733, 139, 748 ], "spans": [ { "bbox": [ 88, 733, 139, 748 ], "type": "text", "content": "基本语法：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 749, 165, 761 ], "type": "text", "angle": 0, "index": 42, "lines": [ { "bbox": [ 88, 749, 167, 762 ], "spans": [ { "bbox": [ 88, 749, 167, 762 ], "type": "text", "content": "SELECT select_list", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 10 }, { "para_blocks": [ { "bbox": [ 86, 79, 174, 91 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 79, 174, 93 ], "spans": [ { "bbox": [ 88, 79, 174, 93 ], "type": "text", "content": "FROM table_sourse", "score": 1.0 } ] } ] }, { "bbox": [ 87, 95, 236, 106 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 95, 236, 108 ], "spans": [ { "bbox": [ 88, 95, 236, 108 ], "type": "text", "content": "WHERE EXPRESSION LIKE ‘STRING’", "score": 1.0 } ] } ] }, { "bbox": [ 88, 111, 96, 121 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 113, 96, 123 ], "spans": [ { "bbox": [ 88, 113, 96, 123 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 125, 313, 138 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 125, 314, 140 ], "spans": [ { "bbox": [ 88, 125, 314, 140 ], "type": "text", "content": "其中，EXPRESSION 为用作选择条件的列或表达式", "score": 1.0 } ] } ] }, { "bbox": [ 88, 143, 96, 153 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 143, 96, 154 ], "spans": [ { "bbox": [ 88, 143, 96, 154 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 157, 273, 169 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 89, 157, 274, 170 ], "spans": [ { "bbox": [ 89, 157, 274, 170 ], "type": "text", "content": "指定的字符串中可以包含通配符，包括：", "score": 1.0 } ] } ] }, { "bbox": [ 89, 173, 249, 186 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 90, 171, 251, 189 ], "spans": [ { "bbox": [ 90, 171, 251, 189 ], "type": "text", "content": "%：代表任意多个字符。例：%jing", "score": 1.0 } ] } ] }, { "bbox": [ 89, 188, 282, 201 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 89, 185, 283, 204 ], "spans": [ { "bbox": [ 89, 185, 283, 204 ], "type": "text", "content": "_（下划线）：代表单个字符。例：_ouse", "score": 1.0 } ] } ] }, { "bbox": [ 89, 203, 309, 217 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 89, 203, 311, 219 ], "spans": [ { "bbox": [ 89, 203, 311, 219 ], "type": "text", "content": "[ ]：代表指定范围内的单个字符。例：[mh]ouse", "score": 1.0 } ] } ] }, { "bbox": [ 89, 219, 342, 232 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 89, 217, 343, 235 ], "spans": [ { "bbox": [ 89, 217, 343, 235 ], "type": "text", "content": "[^ ]：代表不再指定范围内的单个字符。例：[^mh]ouse", "score": 1.0 } ] } ] }, { "bbox": [ 86, 250, 282, 263 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 250, 282, 264 ], "spans": [ { "bbox": [ 88, 250, 282, 264 ], "type": "text", "content": "WHERE子句中，也可以使用逻辑运算符来", "score": 1.0 } ] } ] }, { "bbox": [ 87, 266, 157, 279 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 265, 158, 280 ], "spans": [ { "bbox": [ 88, 265, 158, 280 ], "type": "text", "content": "连接多个条件。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 284, 96, 292 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 285, 96, 294 ], "spans": [ { "bbox": [ 88, 285, 96, 294 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 296, 178, 310 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 89, 297, 179, 310 ], "spans": [ { "bbox": [ 89, 297, 179, 310 ], "type": "text", "content": "主要有逻辑运算符：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 313, 110, 323 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 87, 312, 112, 327 ], "spans": [ { "bbox": [ 87, 312, 112, 327 ], "type": "text", "content": "AND", "score": 1.0 } ] } ] }, { "bbox": [ 88, 328, 104, 338 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 328, 105, 342 ], "spans": [ { "bbox": [ 88, 328, 105, 342 ], "type": "text", "content": "OR", "score": 1.0 } ] } ] }, { "bbox": [ 88, 343, 109, 354 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 86, 343, 111, 358 ], "spans": [ { "bbox": [ 86, 343, 111, 358 ], "type": "text", "content": "NOT", "score": 1.0 } ] } ] }, { "bbox": [ 87, 359, 166, 372 ], "type": "title", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 359, 167, 373 ], "spans": [ { "bbox": [ 88, 359, 167, 373 ], "type": "text", "content": "4.2 SQL 数据删除", "score": 1.0 } ] } ] }, { "bbox": [ 87, 375, 248, 388 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 375, 248, 389 ], "spans": [ { "bbox": [ 89, 375, 248, 389 ], "type": "text", "content": "考核要求：达到“综合应用”层次", "score": 1.0 } ] } ] }, { "bbox": [ 88, 407, 290, 419 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 407, 290, 421 ], "spans": [ { "bbox": [ 88, 407, 290, 421 ], "type": "text", "content": "DELETE FROM 基本表名 [WHERE 条件表达式]", "score": 1.0 } ] } ] }, { "bbox": [ 94, 421, 314, 434 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 95, 422, 314, 436 ], "spans": [ { "bbox": [ 95, 422, 314, 436 ], "type": "text", "content": "（语义：从基本表中删除满足条件表达式的元组）", "score": 1.0 } ] } ] }, { "bbox": [ 88, 437, 207, 449 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 89, 439, 205, 449 ], "spans": [ { "bbox": [ 89, 439, 205, 449 ], "type": "text", "content": "注意带子查询的数据删除", "score": 1.0 } ] } ] }, { "bbox": [ 87, 453, 352, 465 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 89, 454, 352, 466 ], "spans": [ { "bbox": [ 89, 454, 352, 466 ], "type": "text", "content": "示例：求有两门以上不及格课程同学的学号及其平均成绩", "score": 1.0 } ] } ] }, { "bbox": [ 88, 469, 216, 481 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 468, 217, 482 ], "spans": [ { "bbox": [ 88, 468, 217, 482 ], "type": "text", "content": "Select S#, Avg(Score) From SC", "score": 1.0 } ] } ] }, { "bbox": [ 88, 485, 166, 495 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 484, 166, 497 ], "spans": [ { "bbox": [ 88, 484, 145, 497 ], "type": "text", "content": "Where Score", "score": 1.0 }, { "bbox": [ 145, 485, 166, 496 ], "type": "inline_equation", "content": "< 6 0", "score": 0.52 } ] } ] }, { "bbox": [ 88, 500, 226, 512 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 88, 498, 227, 514 ], "spans": [ { "bbox": [ 88, 498, 200, 514 ], "type": "text", "content": "Group by S# Having Count", "score": 1.0 }, { "bbox": [ 201, 500, 223, 512 ], "type": "inline_equation", "content": "^ { ( * ) } ) { > } 2", "score": 0.76 }, { "bbox": [ 223, 498, 227, 514 ], "type": "text", "content": ";", "score": 1.0 } ] } ] }, { "bbox": [ 87, 514, 458, 544 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 88, 514, 458, 529 ], "spans": [ { "bbox": [ 88, 514, 458, 529 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 530, 298, 544 ], "spans": [ { "bbox": [ 88, 530, 298, 544 ], "type": "text", "content": "学所有课程的平均成绩” 。因此正确写法为：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 546, 216, 559 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 545, 217, 560 ], "spans": [ { "bbox": [ 88, 545, 217, 560 ], "type": "text", "content": "Select S#, Avg(Score) From SC", "score": 1.0 } ] } ] }, { "bbox": [ 88, 562, 142, 573 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 88, 561, 143, 575 ], "spans": [ { "bbox": [ 88, 561, 143, 575 ], "type": "text", "content": "Where S# in", "score": 1.0 } ] } ] }, { "bbox": [ 88, 577, 171, 589 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 88, 577, 172, 591 ], "spans": [ { "bbox": [ 88, 577, 172, 591 ], "type": "text", "content": "( Select S# From SC", "score": 1.0 } ] } ] }, { "bbox": [ 88, 593, 166, 604 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 88, 592, 167, 607 ], "spans": [ { "bbox": [ 88, 592, 167, 607 ], "type": "text", "content": "Where Score < 60", "score": 1.0 } ] } ] }, { "bbox": [ 88, 608, 228, 621 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 88, 608, 230, 623 ], "spans": [ { "bbox": [ 88, 608, 200, 623 ], "type": "text", "content": "Group by S# Having Count", "score": 1.0 }, { "bbox": [ 200, 609, 224, 621 ], "type": "inline_equation", "content": "^ { ( * ) } ) { > } 2", "score": 0.6 }, { "bbox": [ 224, 608, 230, 623 ], "type": "text", "content": ")", "score": 1.0 } ] } ] }, { "bbox": [ 88, 625, 142, 636 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 88, 624, 143, 638 ], "spans": [ { "bbox": [ 88, 624, 143, 638 ], "type": "text", "content": "Group by S#", "score": 1.0 } ] } ] }, { "bbox": [ 88, 640, 132, 652 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 87, 640, 133, 655 ], "spans": [ { "bbox": [ 87, 640, 133, 655 ], "type": "text", "content": "交叉连接", "score": 1.0 } ] } ] }, { "bbox": [ 87, 655, 336, 684 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 89, 656, 337, 669 ], "spans": [ { "bbox": [ 89, 656, 337, 669 ], "type": "text", "content": "也叫非限制连接，将两个表不加任何约束的组合起来，", "score": 1.0 } ] }, { "bbox": [ 89, 671, 210, 685 ], "spans": [ { "bbox": [ 89, 671, 210, 685 ], "type": "text", "content": "即两个表的广义笛卡尔积。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 689, 96, 698 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 88, 689, 96, 699 ], "spans": [ { "bbox": [ 88, 689, 96, 699 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 702, 342, 730 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 89, 703, 343, 715 ], "spans": [ { "bbox": [ 89, 703, 343, 715 ], "type": "text", "content": "交叉连接后得到的结果集的行数是两个被连接表的行数", "score": 1.0 } ] }, { "bbox": [ 88, 717, 127, 732 ], "spans": [ { "bbox": [ 88, 717, 127, 732 ], "type": "text", "content": "的乘积。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 735, 96, 744 ], "type": "text", "angle": 0, "index": 37, "lines": [ { "bbox": [ 88, 736, 96, 746 ], "spans": [ { "bbox": [ 88, 736, 96, 746 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 749, 115, 761 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 88, 749, 119, 764 ], "spans": [ { "bbox": [ 88, 749, 119, 764 ], "type": "text", "content": "语法：", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 11 }, { "para_blocks": [ { "type": "code", "bbox": [ 87, 79, 229, 153 ], "blocks": [ { "bbox": [ 87, 79, 229, 153 ], "lines": [ { "bbox": [ 87, 79, 229, 153 ], "spans": [ { "bbox": [ 87, 79, 229, 153 ], "type": "text", "content": "SELECT select_list \nFROM table1 CROSS JOIN table2 \n或 \nSELECT select_list \nFROM table1, table2" } ] } ], "index": 0, "angle": 0, "type": "code_body" } ], "index": 0, "sub_type": "code", "guess_lang": "sql" }, { "bbox": [ 88, 157, 155, 169 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 157, 157, 170 ], "spans": [ { "bbox": [ 88, 157, 157, 170 ], "type": "text", "content": "SQL高级语法：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 173, 117, 184 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 171, 119, 186 ], "spans": [ { "bbox": [ 88, 171, 119, 186 ], "type": "text", "content": "Select", "score": 1.0 } ] } ] }, { "bbox": [ 88, 188, 110, 200 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 86, 187, 113, 205 ], "spans": [ { "bbox": [ 86, 187, 113, 205 ], "type": "text", "content": "列名", "score": 1.0 } ] } ] }, { "bbox": [ 88, 204, 145, 216 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 203, 146, 219 ], "spans": [ { "bbox": [ 88, 203, 146, 219 ], "type": "text", "content": "[ [, 列名] … ]", "score": 1.0 } ] } ] }, { "bbox": [ 88, 220, 194, 232 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 87, 217, 195, 235 ], "spans": [ { "bbox": [ 87, 217, 195, 235 ], "type": "text", "content": "From 表名 1 [NATURAL]", "score": 1.0 } ] } ] }, { "type": "code", "bbox": [ 88, 235, 327, 263 ], "blocks": [ { "bbox": [ 88, 235, 327, 263 ], "lines": [ { "bbox": [ 88, 235, 327, 263 ], "spans": [ { "bbox": [ 88, 235, 327, 263 ], "type": "text", "content": "[INNER|{LEFT|RIGHT|FULL} [OUTER]] JOIN 表名2 {ON" } ] } ], "index": 6, "angle": 0, "type": "code_body" } ], "index": 6, "sub_type": "code", "guess_lang": "txt" }, { "bbox": [ 88, 266, 136, 280 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 87, 264, 138, 281 ], "spans": [ { "bbox": [ 87, 264, 138, 281 ], "type": "text", "content": "连接条件}", "score": 1.0 } ] } ] }, { "bbox": [ 88, 282, 190, 295 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 87, 281, 192, 296 ], "spans": [ { "bbox": [ 87, 281, 192, 296 ], "type": "text", "content": "[ Where 检索条件 ] … ;", "score": 1.0 } ] } ] }, { "bbox": [ 88, 297, 176, 310 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 296, 176, 312 ], "spans": [ { "bbox": [ 88, 296, 176, 312 ], "type": "text", "content": "连接中使用 natural", "score": 1.0 } ] } ] }, { "bbox": [ 88, 312, 426, 388 ], "type": "list", "angle": 0, "index": 13, "blocks": [ { "bbox": [ 88, 312, 426, 341 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 312, 427, 327 ], "spans": [ { "bbox": [ 88, 312, 427, 327 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 328, 174, 342 ], "spans": [ { "bbox": [ 89, 328, 174, 342 ], "type": "text", "content": "共属性只出现一次", "score": 1.0 } ] } ] }, { "bbox": [ 88, 343, 220, 357 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 343, 220, 357 ], "spans": [ { "bbox": [ 88, 344, 97, 356 ], "type": "inline_equation", "content": "\\varnothing", "score": 0.58 }, { "bbox": [ 98, 343, 220, 357 ], "type": "text", "content": "连接中使用 on <连接条件>", "score": 1.0 } ] } ] }, { "bbox": [ 88, 359, 423, 388 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 359, 424, 374 ], "spans": [ { "bbox": [ 88, 359, 424, 374 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 375, 143, 389 ], "spans": [ { "bbox": [ 88, 375, 143, 389 ], "type": "text", "content": "性出现两次", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 89, 391, 171, 404 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 389, 173, 407 ], "spans": [ { "bbox": [ 88, 389, 173, 407 ], "type": "text", "content": "内连接(Inner Join)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 409, 95, 416 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 409, 96, 418 ], "spans": [ { "bbox": [ 88, 409, 96, 418 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 422, 359, 450 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 422, 361, 436 ], "spans": [ { "bbox": [ 88, 422, 361, 436 ], "type": "text", "content": "指定了 INNER 关键字的连接是内连接，内连接按照 ON 所指", "score": 1.0 } ] }, { "bbox": [ 88, 439, 305, 451 ], "spans": [ { "bbox": [ 88, 439, 305, 451 ], "type": "text", "content": "定的连接条件合并两个表，返回满足条件的行。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 455, 95, 463 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 456, 96, 465 ], "spans": [ { "bbox": [ 88, 456, 96, 465 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 468, 362, 497 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 469, 363, 481 ], "spans": [ { "bbox": [ 89, 469, 363, 481 ], "type": "text", "content": "内连接是系统默认的，可以省略INNER关键字。使用内连接", "score": 1.0 } ] }, { "bbox": [ 89, 485, 246, 497 ], "spans": [ { "bbox": [ 89, 485, 246, 497 ], "type": "text", "content": "后仍可使用WHERE子句指定条件。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 502, 95, 510 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 502, 96, 513 ], "spans": [ { "bbox": [ 88, 502, 96, 513 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 515, 330, 542 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 88, 514, 331, 529 ], "spans": [ { "bbox": [ 88, 514, 179, 529 ], "type": "text", "content": "如：<表名1>.<列名", "score": 1.0 }, { "bbox": [ 179, 516, 212, 528 ], "type": "inline_equation", "content": "1 > < > <", "score": 0.78 }, { "bbox": [ 212, 514, 274, 529 ], "type": "text", "content": "表名 2>.<列名", "score": 1.0 }, { "bbox": [ 274, 516, 287, 528 ], "type": "inline_equation", "content": "_ { 2 > }", "score": 0.65 }, { "bbox": [ 287, 514, 331, 529 ], "type": "text", "content": "2024/6/6", "score": 1.0 } ] }, { "bbox": [ 87, 530, 108, 545 ], "spans": [ { "bbox": [ 87, 530, 108, 545 ], "type": "text", "content": "102", "score": 1.0 } ] } ] }, { "bbox": [ 88, 546, 175, 560 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 545, 176, 563 ], "spans": [ { "bbox": [ 88, 545, 176, 563 ], "type": "text", "content": "等值连接(EquiJoin)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 564, 95, 571 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 565, 96, 574 ], "spans": [ { "bbox": [ 88, 565, 96, 574 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 577, 314, 606 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 577, 309, 591 ], "spans": [ { "bbox": [ 88, 577, 114, 591 ], "type": "text", "content": "使用", "score": 1.0 }, { "bbox": [ 115, 578, 130, 589 ], "type": "inline_equation", "content": "^ { 6 6 } = \\upsilon", "score": 0.71 }, { "bbox": [ 130, 577, 309, 591 ], "type": "text", "content": "关系将表连接起来的查询，其查询结果", "score": 1.0 } ] }, { "bbox": [ 89, 594, 315, 607 ], "spans": [ { "bbox": [ 89, 594, 315, 607 ], "type": "text", "content": "中列出被连接表中的所有列，包括其中的重复列。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 611, 95, 618 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 612, 96, 621 ], "spans": [ { "bbox": [ 88, 612, 96, 621 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 624, 132, 637 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 88, 624, 133, 639 ], "spans": [ { "bbox": [ 88, 624, 133, 639 ], "type": "text", "content": "等值连接", "score": 1.0 } ] } ] }, { "bbox": [ 88, 640, 215, 652 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 89, 640, 215, 653 ], "spans": [ { "bbox": [ 89, 640, 152, 653 ], "type": "text", "content": "连接运算符为", "score": 1.0 }, { "bbox": [ 152, 642, 162, 651 ], "type": "inline_equation", "content": "=", "score": 0.84 }, { "bbox": [ 162, 640, 215, 653 ], "type": "text", "content": "的连接操作", "score": 1.0 } ] } ] }, { "bbox": [ 88, 655, 281, 668 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 655, 281, 671 ], "spans": [ { "bbox": [ 88, 655, 171, 671 ], "type": "text", "content": "v [<表名 1>.]<列名", "score": 1.0 }, { "bbox": [ 172, 656, 193, 668 ], "type": "inline_equation", "content": "\\uparrow > =", "score": 0.78 }, { "bbox": [ 193, 655, 267, 671 ], "type": "text", "content": "[<表名 2>.]<列名", "score": 1.0 }, { "bbox": [ 268, 656, 281, 668 ], "type": "inline_equation", "content": "_ { 2 > }", "score": 0.78 } ] } ] }, { "bbox": [ 88, 671, 349, 700 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 89, 671, 350, 684 ], "spans": [ { "bbox": [ 89, 671, 350, 684 ], "type": "text", "content": "任何子句中引用表1和表2中同名属性时，都必须加表名", "score": 1.0 } ] }, { "bbox": [ 89, 688, 336, 700 ], "spans": [ { "bbox": [ 89, 688, 336, 700 ], "type": "text", "content": "前缀。引用唯一属性名时可以加也可以省略表名前缀。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 705, 95, 713 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 88, 705, 96, 715 ], "spans": [ { "bbox": [ 88, 705, 96, 715 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 718, 356, 744 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 89, 717, 357, 731 ], "spans": [ { "bbox": [ 89, 717, 224, 731 ], "type": "text", "content": "表的连接条件经常采用“主码", "score": 1.0 }, { "bbox": [ 224, 719, 232, 729 ], "type": "inline_equation", "content": "\\mathsf { I } \\equiv \\mathsf { I }", "score": 0.68 }, { "bbox": [ 232, 717, 357, 731 ], "type": "text", "content": "外部码”的形式。2024/6/6", "score": 1.0 } ] }, { "bbox": [ 88, 733, 108, 747 ], "spans": [ { "bbox": [ 88, 733, 108, 747 ], "type": "text", "content": "103", "score": 1.0 } ] } ] }, { "bbox": [ 88, 751, 95, 759 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 88, 751, 96, 761 ], "spans": [ { "bbox": [ 88, 751, 96, 761 ], "type": "text", "content": "v", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 12 }, { "para_blocks": [ { "bbox": [ 87, 79, 116, 91 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 78, 119, 95 ], "spans": [ { "bbox": [ 88, 78, 119, 95 ], "type": "text", "content": "语法：", "score": 1.0 } ] } ] }, { "bbox": [ 87, 95, 166, 106 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 94, 167, 108 ], "spans": [ { "bbox": [ 88, 94, 167, 108 ], "type": "text", "content": "SELECT select_list", "score": 1.0 } ] } ] }, { "bbox": [ 87, 109, 235, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 110, 236, 124 ], "spans": [ { "bbox": [ 88, 110, 236, 124 ], "type": "text", "content": "FROM table1 [INNER] JOIN table2", "score": 1.0 } ] } ] }, { "bbox": [ 87, 126, 245, 137 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 89, 126, 245, 138 ], "spans": [ { "bbox": [ 89, 126, 245, 138 ], "type": "text", "content": "ON table1.column1=table2.column2", "score": 1.0 } ] } ] }, { "bbox": [ 87, 142, 101, 153 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 142, 102, 156 ], "spans": [ { "bbox": [ 88, 142, 102, 156 ], "type": "text", "content": "和", "score": 1.0 } ] } ] }, { "bbox": [ 87, 157, 165, 169 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 88, 156, 167, 170 ], "spans": [ { "bbox": [ 88, 156, 167, 170 ], "type": "text", "content": "SELECT select_list", "score": 1.0 } ] } ] }, { "bbox": [ 87, 174, 185, 185 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 88, 174, 186, 186 ], "spans": [ { "bbox": [ 88, 174, 186, 186 ], "type": "text", "content": "FROM table1 ，table2", "score": 1.0 } ] } ] }, { "bbox": [ 87, 188, 262, 200 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 88, 188, 264, 200 ], "spans": [ { "bbox": [ 88, 188, 264, 200 ], "type": "text", "content": "WHERE table1.column1=table2.column2", "score": 1.0 } ] } ] }, { "bbox": [ 86, 203, 411, 217 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 88, 202, 411, 218 ], "spans": [ { "bbox": [ 88, 202, 411, 218 ], "type": "text", "content": "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)", "score": 1.0 } ] } ] }, { "bbox": [ 87, 220, 117, 230 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 218, 119, 232 ], "spans": [ { "bbox": [ 88, 218, 119, 232 ], "type": "text", "content": "Select", "score": 1.0 } ] } ] }, { "bbox": [ 87, 235, 198, 246 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 234, 198, 248 ], "spans": [ { "bbox": [ 88, 234, 198, 248 ], "type": "text", "content": "Sname From Student, SC", "score": 1.0 } ] } ] }, { "bbox": [ 87, 250, 279, 261 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 250, 280, 263 ], "spans": [ { "bbox": [ 88, 250, 157, 263 ], "type": "text", "content": "Where Student.", "score": 1.0 }, { "bbox": [ 158, 250, 203, 262 ], "type": "inline_equation", "content": "\\mathsf { S } \\# = \\mathsf { S C } . \\mathsf { S } \\#", "score": 0.66 }, { "bbox": [ 203, 250, 280, 263 ], "type": "text", "content": "and SC.C# = ‘001’", "score": 1.0 } ] } ] }, { "bbox": [ 87, 266, 182, 278 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 265, 184, 280 ], "spans": [ { "bbox": [ 88, 265, 184, 280 ], "type": "text", "content": "Order By Score DESC;", "score": 1.0 } ] } ] }, { "bbox": [ 86, 281, 429, 294 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 282, 430, 296 ], "spans": [ { "bbox": [ 88, 282, 98, 294 ], "type": "inline_equation", "content": "\\varnothing", "score": 0.63 }, { "bbox": [ 98, 282, 430, 296 ], "type": "text", "content": "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", "score": 1.0 } ] } ] }, { "bbox": [ 87, 297, 198, 309 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 298, 198, 310 ], "spans": [ { "bbox": [ 89, 298, 198, 310 ], "type": "text", "content": "该 属性是属于哪一个表", "score": 1.0 } ] } ] }, { "bbox": [ 86, 312, 411, 326 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 312, 411, 327 ], "spans": [ { "bbox": [ 88, 312, 411, 327 ], "type": "text", "content": "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)", "score": 1.0 } ] } ] }, { "bbox": [ 87, 328, 117, 339 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 327, 119, 342 ], "spans": [ { "bbox": [ 88, 327, 119, 342 ], "type": "text", "content": "Select", "score": 1.0 } ] } ] }, { "bbox": [ 87, 343, 232, 355 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 343, 233, 357 ], "spans": [ { "bbox": [ 88, 343, 233, 357 ], "type": "text", "content": "Sname From Student, SC, Course", "score": 1.0 } ] } ] }, { "bbox": [ 87, 359, 120, 370 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 88, 358, 121, 373 ], "spans": [ { "bbox": [ 88, 358, 121, 373 ], "type": "text", "content": "Where", "score": 1.0 } ] } ] }, { "bbox": [ 86, 375, 367, 387 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 375, 368, 390 ], "spans": [ { "bbox": [ 88, 375, 125, 390 ], "type": "text", "content": "Student.", "score": 1.0 }, { "bbox": [ 126, 376, 171, 387 ], "type": "inline_equation", "content": "S \\# = \\Im \\mathbb { C } . S \\#", "score": 0.84 }, { "bbox": [ 171, 375, 215, 390 ], "type": "text", "content": "and SC.C#", "score": 1.0 }, { "bbox": [ 215, 377, 224, 386 ], "type": "inline_equation", "content": "\\equiv", "score": 0.56 }, { "bbox": [ 224, 375, 320, 390 ], "type": "text", "content": "Course.C# and Cname", "score": 1.0 }, { "bbox": [ 321, 376, 329, 386 ], "type": "inline_equation", "content": "\\equiv", "score": 0.78 }, { "bbox": [ 330, 375, 368, 390 ], "type": "text", "content": "‘数据库", "score": 1.0 } ] } ] }, { "bbox": [ 87, 391, 182, 402 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 88, 390, 184, 405 ], "spans": [ { "bbox": [ 88, 390, 184, 405 ], "type": "text", "content": "Order By Score DESC;", "score": 1.0 } ] } ] }, { "bbox": [ 88, 406, 132, 418 ], "type": "title", "angle": 0, "index": 21, "lines": [ { "bbox": [ 89, 407, 133, 421 ], "spans": [ { "bbox": [ 89, 407, 133, 421 ], "type": "text", "content": "自然连接", "score": 1.0 } ] } ] }, { "bbox": [ 87, 422, 324, 434 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 89, 423, 325, 435 ], "spans": [ { "bbox": [ 89, 423, 325, 435 ], "type": "text", "content": "等值连接的一种特殊情况，自动判断相同名称的列，", "score": 1.0 } ] } ] }, { "bbox": [ 87, 437, 304, 449 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 89, 438, 305, 451 ], "spans": [ { "bbox": [ 89, 438, 305, 451 ], "type": "text", "content": "而后形成匹配，把目标列中重复的属性列去掉。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 453, 261, 465 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 451, 262, 468 ], "spans": [ { "bbox": [ 88, 451, 116, 468 ], "type": "text", "content": "<表名", "score": 1.0 }, { "bbox": [ 117, 454, 136, 465 ], "type": "inline_equation", "content": "\\uparrow > . <", "score": 0.53 }, { "bbox": [ 137, 451, 158, 468 ], "type": "text", "content": "列名", "score": 1.0 }, { "bbox": [ 158, 454, 186, 465 ], "type": "inline_equation", "content": "\\gimel = { < }", "score": 0.91 }, { "bbox": [ 186, 451, 207, 468 ], "type": "text", "content": "表名", "score": 1.0 }, { "bbox": [ 207, 454, 227, 465 ], "type": "inline_equation", "content": "_ { 2 > . < }", "score": 0.59 }, { "bbox": [ 227, 451, 248, 468 ], "type": "text", "content": "<列名", "score": 1.0 }, { "bbox": [ 248, 454, 262, 465 ], "type": "inline_equation", "content": "_ { 2 > }", "score": 0.79 } ] } ] }, { "bbox": [ 87, 470, 95, 479 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 88, 470, 96, 481 ], "spans": [ { "bbox": [ 88, 470, 96, 481 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 484, 273, 497 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 88, 482, 274, 499 ], "spans": [ { "bbox": [ 88, 482, 274, 499 ], "type": "text", "content": "有些 DBMS 产品，如 SQL Server，不支持", "score": 1.0 } ] } ] }, { "bbox": [ 87, 500, 311, 513 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 500, 312, 513 ], "spans": [ { "bbox": [ 88, 500, 312, 513 ], "type": "text", "content": "NATURAL JOIN连接符，故不能直接实现自然连接", "score": 1.0 } ] } ] }, { "bbox": [ 87, 530, 208, 544 ], "type": "title", "angle": 0, "index": 28, "lines": [ { "bbox": [ 89, 530, 210, 546 ], "spans": [ { "bbox": [ 89, 530, 210, 546 ], "type": "text", "content": "非等值连接 (Non-EquiJoin)", "score": 1.0 } ] } ] }, { "bbox": [ 87, 549, 95, 556 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 88, 550, 96, 559 ], "spans": [ { "bbox": [ 88, 550, 96, 559 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 561, 143, 575 ], "type": "title", "angle": 0, "index": 30, "lines": [ { "bbox": [ 88, 562, 143, 576 ], "spans": [ { "bbox": [ 88, 562, 143, 576 ], "type": "text", "content": "非等值连接", "score": 1.0 } ] } ] }, { "bbox": [ 87, 577, 226, 590 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 89, 577, 226, 591 ], "spans": [ { "bbox": [ 89, 577, 163, 591 ], "type": "text", "content": "连接运算符不为", "score": 1.0 }, { "bbox": [ 163, 579, 172, 588 ], "type": "inline_equation", "content": "=", "score": 0.84 }, { "bbox": [ 173, 577, 226, 591 ], "type": "text", "content": "的连接操作", "score": 1.0 } ] } ] }, { "bbox": [ 87, 596, 95, 603 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 88, 596, 96, 606 ], "spans": [ { "bbox": [ 88, 596, 96, 606 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 608, 115, 621 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 86, 608, 117, 624 ], "spans": [ { "bbox": [ 86, 608, 117, 624 ], "type": "text", "content": "形式：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 624, 333, 638 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 90, 623, 334, 640 ], "spans": [ { "bbox": [ 90, 623, 167, 640 ], "type": "text", "content": "[<表名 1>.]<列名", "score": 1.0 }, { "bbox": [ 167, 625, 187, 637 ], "type": "inline_equation", "content": "\\ L _ { 1 } > <", "score": 0.87 }, { "bbox": [ 188, 623, 238, 640 ], "type": "text", "content": "比较运算符", "score": 1.0 }, { "bbox": [ 238, 625, 255, 637 ], "type": "inline_equation", "content": "> [ <", "score": 0.74 }, { "bbox": [ 255, 623, 276, 640 ], "type": "text", "content": "<表名", "score": 1.0 }, { "bbox": [ 276, 624, 299, 637 ], "type": "inline_equation", "content": "2 { > } . ] <", "score": 0.56 }, { "bbox": [ 300, 623, 320, 640 ], "type": "text", "content": "<列名", "score": 1.0 }, { "bbox": [ 321, 625, 334, 637 ], "type": "inline_equation", "content": "_ { 2 > }", "score": 0.73 } ] } ] }, { "bbox": [ 88, 640, 260, 652 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 88, 640, 261, 655 ], "spans": [ { "bbox": [ 88, 640, 146, 655 ], "type": "text", "content": "比较运算符：", "score": 1.0 }, { "bbox": [ 147, 640, 261, 652 ], "type": "inline_equation", "content": "\\therefore x _ { 1 } > = 1 < = 1 1 = ( < 2 )", "score": 0.67 } ] } ] }, { "bbox": [ 87, 655, 311, 668 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 88, 654, 311, 671 ], "spans": [ { "bbox": [ 88, 654, 164, 671 ], "type": "text", "content": "[<表名 1>.]<列名", "score": 1.0 }, { "bbox": [ 164, 656, 177, 667 ], "type": "inline_equation", "content": "\\Im \\succ", "score": 0.84 }, { "bbox": [ 178, 654, 253, 671 ], "type": "text", "content": "BETWEEN [<表名", "score": 1.0 }, { "bbox": [ 253, 656, 284, 669 ], "type": "inline_equation", "content": "2 > . ] < \\bar { \\mathcal { G } } ^ { \\mid }", "score": 0.52 }, { "bbox": [ 285, 654, 298, 671 ], "type": "text", "content": "名", "score": 1.0 }, { "bbox": [ 298, 656, 311, 668 ], "type": "inline_equation", "content": "_ { 2 > }", "score": 0.83 } ] } ] }, { "bbox": [ 87, 671, 198, 684 ], "type": "text", "angle": 0, "index": 37, "lines": [ { "bbox": [ 88, 670, 199, 685 ], "spans": [ { "bbox": [ 88, 670, 186, 685 ], "type": "text", "content": "AND [<表名 2>.]<列名", "score": 1.0 }, { "bbox": [ 186, 671, 199, 683 ], "type": "inline_equation", "content": "\\mathfrak { 3 } \\mathfrak { > }", "score": 0.83 } ] } ] }, { "bbox": [ 86, 687, 333, 699 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 89, 687, 333, 701 ], "spans": [ { "bbox": [ 89, 687, 333, 701 ], "type": "text", "content": "求既学过“001”号课⼜学过 “002”号课的所有学生的", "score": 1.0 } ] } ] }, { "bbox": [ 87, 702, 110, 714 ], "type": "text", "angle": 0, "index": 39, "lines": [ { "bbox": [ 87, 702, 113, 719 ], "spans": [ { "bbox": [ 87, 702, 113, 719 ], "type": "text", "content": "学号", "score": 1.0 } ] } ] }, { "bbox": [ 87, 719, 116, 729 ], "type": "text", "angle": 0, "index": 40, "lines": [ { "bbox": [ 88, 717, 119, 731 ], "spans": [ { "bbox": [ 88, 717, 119, 731 ], "type": "text", "content": "Select", "score": 1.0 } ] } ] }, { "bbox": [ 87, 734, 113, 744 ], "type": "text", "angle": 0, "index": 41, "lines": [ { "bbox": [ 86, 732, 116, 747 ], "spans": [ { "bbox": [ 86, 732, 116, 747 ], "type": "text", "content": "S1.S#", "score": 1.0 } ] } ] }, { "bbox": [ 87, 749, 154, 761 ], "type": "text", "angle": 0, "index": 42, "lines": [ { "bbox": [ 88, 748, 155, 762 ], "spans": [ { "bbox": [ 88, 748, 155, 762 ], "type": "text", "content": "From SC S1, SC", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 13 }, { "para_blocks": [ { "bbox": [ 87, 79, 132, 89 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 79, 134, 93 ], "spans": [ { "bbox": [ 88, 79, 134, 93 ], "type": "text", "content": "S2 Where", "score": 1.0 } ] } ] }, { "bbox": [ 87, 95, 165, 105 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 95, 166, 107 ], "spans": [ { "bbox": [ 88, 95, 146, 106 ], "type": "inline_equation", "content": "\\mathsf { S } \\mathsf { 1 } . \\mathsf { S } \\# = \\mathsf { S } 2 . \\mathsf { S } \\#", "score": 0.88 }, { "bbox": [ 147, 95, 166, 107 ], "type": "text", "content": "and", "score": 1.0 } ] } ] }, { "bbox": [ 88, 110, 140, 121 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 110, 139, 121 ], "spans": [ { "bbox": [ 88, 110, 139, 121 ], "type": "inline_equation", "content": "\\mathsf { S } 1 . 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], "type": "text", "content": "学号", "score": 1.0 } ] } ] }, { "bbox": [ 87, 188, 252, 200 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 88, 187, 254, 201 ], "spans": [ { "bbox": [ 88, 187, 254, 201 ], "type": "text", "content": "Select S1.S# From SC S1, SC S2 Where", "score": 1.0 } ] } ] }, { "bbox": [ 88, 203, 218, 215 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 88, 203, 218, 217 ], "spans": [ { "bbox": [ 88, 203, 146, 215 ], "type": "inline_equation", "content": "\\mathsf { S } \\mathsf { 1 } . \\mathsf { S } \\# = \\mathsf { S } 2 . \\mathsf { S } \\#", "score": 0.85 }, { "bbox": [ 147, 203, 218, 217 ], "type": "text", "content": "and S1.C#=‘001’", "score": 1.0 } ] } ] }, { "bbox": [ 88, 220, 107, 230 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 86, 219, 108, 232 ], "spans": [ { "bbox": [ 86, 219, 108, 232 ], "type": "text", "content": "and", "score": 1.0 } ] } ] }, { "bbox": [ 88, 235, 248, 247 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 89, 232, 249, 250 ], "spans": [ { "bbox": [ 89, 235, 140, 247 ], "type": "inline_equation", "content": "\\mathsf { S } 2 . \\mathsf { C } \\# { = } ^ { \\prime } 0 0 2 ^ { \\prime }", "score": 0.84 }, { "bbox": [ 141, 232, 198, 250 ], "type": "text", "content": "and S1.Score", "score": 1.0 }, { "bbox": [ 198, 237, 207, 245 ], "type": "inline_equation", "content": ">", "score": 0.68 }, { "bbox": [ 207, 232, 249, 250 ], "type": "text", "content": "S2.Score;", "score": 1.0 } ] } ] }, { "bbox": [ 88, 251, 95, 260 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 251, 96, 263 ], "spans": [ { "bbox": [ 88, 251, 96, 263 ], "type": "text", "content": "S", "score": 1.0 } ] } ] }, { "bbox": [ 88, 265, 121, 279 ], "type": "title", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 265, 123, 282 ], "spans": [ { "bbox": [ 88, 265, 123, 282 ], "type": "text", "content": "外连接", "score": 1.0 } ] } ] }, { "bbox": [ 88, 284, 95, 291 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 284, 96, 295 ], "spans": [ { "bbox": [ 88, 284, 96, 295 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 296, 291, 341 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 297, 292, 311 ], "spans": [ { "bbox": [ 88, 297, 292, 311 ], "type": "text", "content": "指定了OUTER关键字的为外连接，外连接的", "score": 1.0 } ] }, { "bbox": [ 89, 314, 290, 327 ], "spans": [ { "bbox": [ 89, 314, 290, 327 ], "type": "text", "content": "结果表不但包含满足连接条件的行，还包括", "score": 1.0 } ] }, { "bbox": [ 89, 329, 179, 342 ], "spans": [ { "bbox": [ 89, 329, 179, 342 ], "type": "text", "content": "相应表中的所有行。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 346, 95, 354 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 347, 96, 357 ], "spans": [ { "bbox": [ 88, 347, 96, 357 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 359, 289, 403 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 360, 290, 373 ], "spans": [ { "bbox": [ 88, 360, 290, 373 ], "type": "text", "content": "外连接中，可以只限制一个表，而对另一个", "score": 1.0 } ] }, { "bbox": [ 88, 375, 279, 389 ], "spans": [ { "bbox": [ 88, 375, 279, 389 ], "type": "text", "content": "表不加限制（即所有的行都出现在结果集", "score": 1.0 } ] }, { "bbox": [ 88, 390, 118, 406 ], "spans": [ { "bbox": [ 88, 390, 118, 406 ], "type": "text", "content": "中）。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 408, 95, 416 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 409, 96, 419 ], "spans": [ { "bbox": [ 88, 409, 96, 419 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 421, 293, 434 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 422, 294, 437 ], "spans": [ { "bbox": [ 89, 422, 294, 437 ], "type": "text", "content": "外连接分为左外连接、右外连接和全外连接。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 453, 174, 466 ], "type": "title", "angle": 0, "index": 19, "lines": [ { "bbox": [ 89, 451, 176, 469 ], "spans": [ { "bbox": [ 89, 451, 176, 469 ], "type": "text", "content": "自身连接(Self-Join)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 470, 95, 479 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 88, 470, 96, 481 ], "spans": [ { "bbox": [ 88, 470, 96, 481 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 483, 373, 513 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 89, 484, 374, 497 ], "spans": [ { "bbox": [ 89, 484, 374, 497 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 501, 147, 513 ], "spans": [ { "bbox": [ 88, 501, 147, 513 ], "type": "text", "content": "行连接起来。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 518, 95, 525 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 518, 96, 528 ], "spans": [ { "bbox": [ 88, 518, 96, 528 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 530, 283, 544 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 89, 531, 283, 544 ], "spans": [ { "bbox": [ 89, 531, 283, 544 ], "type": "text", "content": "可看作一张表的两个副本之间进行的连接。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 549, 95, 556 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 550, 96, 560 ], "spans": [ { "bbox": [ 88, 550, 96, 560 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 87, 561, 325, 575 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 89, 563, 326, 576 ], "spans": [ { "bbox": [ 89, 563, 326, 576 ], "type": "text", "content": "必须为表指定两个别名，使之在逻辑上成为两张表。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 580, 95, 588 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 88, 581, 96, 591 ], "spans": [ { "bbox": [ 88, 581, 96, 591 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 593, 342, 618 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 593, 342, 607 ], "spans": [ { "bbox": [ 88, 593, 342, 607 ], "type": "text", "content": "由于所有属性名都是同名属性，因此必须使用别名前缀", "score": 1.0 } ] }, { "bbox": [ 87, 610, 96, 623 ], "spans": [ { "bbox": [ 87, 610, 96, 623 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 624, 271, 637 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 88, 623, 271, 640 ], "spans": [ { "bbox": [ 88, 623, 271, 640 ], "type": "text", "content": "例 36.查询 Employee 表中的同姓的职工。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 640, 210, 651 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 88, 640, 211, 653 ], "spans": [ { "bbox": [ 88, 640, 211, 653 ], "type": "text", "content": "SELECT e1.Ename,e2.Ename", "score": 1.0 } ] } ] }, { "bbox": [ 88, 655, 255, 667 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 88, 655, 256, 669 ], "spans": [ { "bbox": [ 88, 655, 256, 669 ], "type": "text", "content": "FROM Employee e1 JOIN Employee e2", "score": 1.0 } ] } ] }, { "bbox": [ 88, 671, 252, 683 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 88, 670, 254, 686 ], "spans": [ { "bbox": [ 88, 670, 254, 686 ], "type": "text", "content": "ON left(e1.Ename,1)=left(e2.Ename,1)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 687, 188, 698 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 88, 686, 189, 700 ], "spans": [ { "bbox": [ 88, 686, 189, 700 ], "type": "text", "content": "WHERE e1.EnoAVG(Age);", "score": 1.0 } ] } ] }, { "bbox": [ 87, 110, 143, 123 ], "type": "title", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 110, 143, 125 ], "spans": [ { "bbox": [ 88, 110, 143, 125 ], "type": "text", "content": "相关子查询", "score": 1.0 } ] } ] }, { "bbox": [ 87, 127, 96, 137 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 128, 96, 138 ], "spans": [ { "bbox": [ 88, 128, 96, 138 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 86, 141, 290, 170 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 142, 290, 154 ], "spans": [ { "bbox": [ 88, 142, 290, 154 ], "type": "text", "content": "执行依赖于外部查询，多数情况下是在子查", "score": 1.0 } ] }, { "bbox": [ 89, 158, 277, 169 ], "spans": [ { "bbox": [ 89, 158, 277, 169 ], "type": "text", "content": "询的WHERE子句中引用了外部查询的表。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 174, 96, 184 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 88, 175, 96, 185 ], "spans": [ { "bbox": [ 88, 175, 96, 185 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 86, 187, 290, 216 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 89, 188, 290, 201 ], "spans": [ { "bbox": [ 89, 188, 290, 201 ], "type": "text", "content": "可以使用EXISTS关键字来判断查询结果中是", "score": 1.0 } ] }, { "bbox": [ 89, 204, 288, 217 ], "spans": [ { "bbox": [ 89, 204, 288, 217 ], "type": "text", "content": "否存在数据，EXISTS在一个子查询至少返回", "score": 1.0 } ] } ] }, { "bbox": [ 87, 219, 147, 232 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 88, 218, 148, 234 ], "spans": [ { "bbox": [ 88, 218, 148, 234 ], "type": "text", "content": "一行时成立。", "score": 1.0 } ] } ] }, { "type": "image", "bbox": [ 90, 231, 595, 572 ], "blocks": [ { "bbox": [ 90, 231, 595, 572 ], "lines": [ { "bbox": [ 90, 231, 595, 572 ], "spans": [ { "bbox": [ 90, 231, 595, 572 ], "type": "image", "image_path": "9befa48b9bdf61690405bec38c2b72f386915c759717198cd755efd254411539.jpg" } ] } ], "index": 8, "angle": 0, "type": "image_body" } ], "index": 8 } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 16 }, { "para_blocks": [ { "bbox": [ 328, 143, 536, 187 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 324, 139, 540, 192 ], "spans": [ { "bbox": [ 324, 139, 540, 192 ], "type": "text", "content": "索引的概念", "score": 1.0 } ] } ] }, { "bbox": [ 161, 198, 595, 260 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 164, 196, 595, 219 ], "spans": [ { "bbox": [ 164, 196, 595, 219 ], "type": "text", "content": "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", "score": 0.998 } ] }, { "bbox": [ 164, 221, 595, 238 ], "spans": [ { "bbox": [ 164, 221, 595, 238 ], "type": "text", "content": "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", "score": 0.998 } ] }, { "bbox": [ 162, 242, 444, 260 ], "spans": [ { "bbox": [ 162, 242, 444, 260 ], "type": "text", "content": "entries)组成，每一索引项又由两部分构成：", "score": 0.991 } ] } ] }, { "bbox": [ 161, 264, 595, 380 ], "type": "list", "angle": 0, "index": 5, "blocks": [ { "bbox": [ 161, 264, 595, 304 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 163, 263, 595, 281 ], "spans": [ { "bbox": [ 163, 263, 595, 281 ], "type": "text", "content": "√索引字段：由Table中某些列(通常是一列)中的值串接而成。索引", "score": 0.986 } ] }, { "bbox": [ 163, 284, 549, 304 ], "spans": [ { "bbox": [ 163, 284, 549, 304 ], "type": "text", "content": "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。", "score": 0.999 } ] } ] }, { "bbox": [ 161, 310, 595, 352 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 165, 310, 595, 327 ], "spans": [ { "bbox": [ 165, 310, 595, 327 ], "type": "text", "content": "√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", "score": 0.997 } ] }, { "bbox": [ 163, 334, 319, 352 ], "spans": [ { "bbox": [ 163, 334, 319, 352 ], "type": "text", "content": "条在书籍、词典中出现的页码。", "score": 0.997 } ] } ] }, { "bbox": [ 162, 359, 595, 380 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 164, 359, 595, 380 ], "spans": [ { "bbox": [ 164, 359, 595, 380 ], "type": "text", "content": "·存储索引项的文件为索引文件，相对应，基本表又称为主文", "score": 0.981 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 205, 408, 370, 428 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 203, 407, 373, 431 ], "spans": [ { "bbox": [ 203, 407, 291, 428 ], "type": "text", "content": "Index-field", "score": 0.997 }, { "bbox": [ 309, 407, 373, 431 ], "type": "text", "content": "pointer", "score": 0.999 } ] } ] }, { "bbox": [ 214, 485, 264, 528 ], "type": "title", "angle": 0, "index": 7, "lines": [ { "bbox": [ 213, 484, 261, 503 ], "spans": [ { "bbox": [ 213, 484, 261, 503 ], "type": "text", "content": "Index", "score": 0.993 } ] }, { "bbox": [ 213, 509, 265, 529 ], "spans": [ { "bbox": [ 213, 509, 265, 529 ], "type": "text", "content": "索引文", "score": 0.999 } ] } ] }, { "type": "table", "bbox": [ 268, 437, 595, 528 ], "blocks": [ { "bbox": [ 268, 437, 595, 528 ], "lines": [ { "bbox": [ 268, 437, 595, 528 ], "spans": [ { "bbox": [ 268, 437, 595, 528 ], "type": "table", "html": "
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
", "image_path": "4b97ea5dcd26b38d182a062114c55b6b48f9d40d78c8196017d40071091cbbca.jpg" } ] } ], "index": 8, "angle": 0, "type": "table_body" } ], "index": 8 }, { "bbox": [ 86, 530, 149, 544 ], "type": "title", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 530, 149, 545 ], "spans": [ { "bbox": [ 88, 530, 149, 545 ], "type": "text", "content": "4.3 数据修改", "score": 1.0 } ] } ] }, { "bbox": [ 87, 546, 248, 560 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 89, 546, 248, 560 ], "spans": [ { "bbox": [ 89, 546, 248, 560 ], "type": "text", "content": "考核要求：达到“综合应用”层次", "score": 1.0 } ] } ] }, { "bbox": [ 86, 577, 168, 590 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 577, 169, 592 ], "spans": [ { "bbox": [ 88, 577, 169, 592 ], "type": "text", "content": "UPDATE 基本表名", "score": 1.0 } ] } ] }, { "bbox": [ 86, 593, 261, 607 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 592, 262, 608 ], "spans": [ { "bbox": [ 88, 592, 126, 608 ], "type": "text", "content": "SET 列名", "score": 1.0 }, { "bbox": [ 127, 595, 134, 605 ], "type": "inline_equation", "content": "=", "score": 0.75 }, { "bbox": [ 134, 592, 201, 608 ], "type": "text", "content": "值表达式,[列名", "score": 1.0 }, { "bbox": [ 201, 595, 208, 604 ], "type": "inline_equation", "content": "=", "score": 0.71 }, { "bbox": [ 208, 592, 262, 608 ], "type": "text", "content": "值表达式...]", "score": 1.0 } ] } ] }, { "bbox": [ 87, 608, 183, 622 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 608, 184, 624 ], "spans": [ { "bbox": [ 88, 608, 184, 624 ], "type": "text", "content": "[WHERE 条件表达式]", "score": 1.0 } ] } ] }, { "bbox": [ 86, 624, 505, 653 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 624, 505, 637 ], "spans": [ { "bbox": [ 89, 624, 505, 637 ], "type": "text", "content": "(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", "score": 1.0 } ] }, { "bbox": [ 88, 638, 107, 656 ], "spans": [ { "bbox": [ 88, 638, 107, 656 ], "type": "text", "content": "出）", "score": 1.0 } ] } ] }, { "bbox": [ 87, 655, 206, 668 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 89, 656, 205, 668 ], "spans": [ { "bbox": [ 89, 656, 205, 668 ], "type": "text", "content": "注意带子查询的数据更新", "score": 1.0 } ] } ] }, { "bbox": [ 87, 687, 158, 699 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 687, 161, 700 ], "spans": [ { "bbox": [ 88, 687, 161, 700 ], "type": "text", "content": "(1)视图的创建：", "score": 1.0 } ] } ] }, { "bbox": [ 87, 702, 309, 715 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 702, 309, 716 ], "spans": [ { "bbox": [ 88, 702, 309, 716 ], "type": "text", "content": "CREATE VIEW 视图名(列名表) AS SELECT 查询语句", "score": 1.0 } ] } ] }, { "bbox": [ 88, 717, 158, 730 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 88, 718, 160, 731 ], "spans": [ { "bbox": [ 88, 718, 160, 731 ], "type": "text", "content": "(2)视图的撤消：", "score": 1.0 } ] } ] }, { "bbox": [ 87, 734, 173, 746 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 733, 174, 748 ], "spans": [ { "bbox": [ 88, 733, 174, 748 ], "type": "text", "content": "DROP VIEW 视图名", "score": 1.0 } ] } ] }, { "bbox": [ 90, 749, 135, 761 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 90, 749, 136, 764 ], "spans": [ { "bbox": [ 90, 749, 136, 764 ], "type": "text", "content": "语句格式", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 17 }, { "para_blocks": [ { "bbox": [ 86, 79, 254, 92 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 79, 255, 92 ], "spans": [ { "bbox": [ 88, 79, 255, 92 ], "type": "text", "content": "CREATE VIEW <视图名> [<列名清单>]", "score": 1.0 } ] } ] }, { "bbox": [ 87, 95, 145, 107 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 87, 94, 147, 109 ], "spans": [ { "bbox": [ 87, 94, 147, 109 ], "type": "text", "content": "AS <子查询>", "score": 1.0 } ] } ] }, { "bbox": [ 87, 110, 189, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 110, 190, 125 ], "spans": [ { "bbox": [ 88, 110, 190, 125 ], "type": "text", "content": "[WITH CHECK OPTION]", "score": 1.0 } ] } ] }, { "bbox": [ 88, 128, 95, 136 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 128, 96, 139 ], "spans": [ { "bbox": [ 88, 128, 96, 139 ], "type": "text", "content": "v", "score": 1.0 } ] } ] }, { "bbox": [ 88, 141, 111, 153 ], "type": "title", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 141, 113, 157 ], "spans": [ { "bbox": [ 88, 141, 113, 157 ], "type": "text", "content": "说明", "score": 1.0 } ] } ] }, { "bbox": [ 89, 157, 254, 169 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 92, 157, 255, 171 ], "spans": [ { "bbox": [ 92, 157, 127, 171 ], "type": "text", "content": "<视图名", "score": 1.0 }, { "bbox": [ 127, 159, 135, 169 ], "type": "inline_equation", "content": ">", "score": 0.56 }, { "bbox": [ 135, 157, 255, 171 ], "type": "text", "content": "给出所定义的视图的名称。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 172, 411, 184 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 91, 173, 412, 186 ], "spans": [ { "bbox": [ 91, 173, 412, 186 ], "type": "text", "content": "<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，", "score": 1.0 } ] } ] }, { "bbox": [ 87, 188, 380, 200 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 89, 188, 380, 202 ], "spans": [ { "bbox": [ 89, 188, 380, 202 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 203, 365, 216 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 90, 201, 367, 219 ], "spans": [ { "bbox": [ 90, 201, 367, 219 ], "type": "text", "content": "<子查询>为任一合法 SELECT 语句（但一般不含有 ORDER BY，", "score": 1.0 } ] } ] }, { "bbox": [ 87, 220, 189, 232 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 217, 192, 235 ], "spans": [ { "bbox": [ 88, 217, 192, 235 ], "type": "text", "content": "UNION 等语法成分）。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 235, 351, 247 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 91, 235, 353, 250 ], "spans": [ { "bbox": [ 91, 235, 353, 250 ], "type": "text", "content": "有[WITH CHECK OPTION]时，则今后对此视图进行 INSERT、", "score": 1.0 } ] } ] }, { "bbox": [ 87, 250, 392, 262 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 250, 394, 264 ], "spans": [ { "bbox": [ 88, 250, 394, 264 ], "type": "text", "content": "UPDATE和DELETE操作时，系统自动检查是否符合原定义视图子查", "score": 1.0 } ] } ] }, { "bbox": [ 87, 266, 188, 279 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 89, 266, 188, 280 ], "spans": [ { "bbox": [ 89, 266, 188, 280 ], "type": "text", "content": "询中的<条件表达式>。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 281, 166, 294 ], "type": "title", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 281, 167, 295 ], "spans": [ { "bbox": [ 88, 281, 167, 295 ], "type": "text", "content": "4.4.2 视图的更新", "score": 1.0 } ] } ] }, { "bbox": [ 86, 296, 509, 310 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 297, 511, 310 ], "spans": [ { "bbox": [ 89, 297, 511, 310 ], "type": "text", "content": "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：", "score": 1.0 } ] } ] }, { "bbox": [ 104, 328, 414, 356 ], "type": "list", "angle": 0, "index": 17, "blocks": [ { "bbox": [ 104, 328, 414, 341 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 117, 328, 415, 343 ], "spans": [ { "bbox": [ 117, 328, 415, 343 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 104, 343, 381, 356 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 119, 344, 383, 357 ], "spans": [ { "bbox": [ 119, 344, 383, 357 ], "type": "text", "content": "如果导出的视图使用了分组和聚合操作，也不允许更新。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 86, 359, 504, 387 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 361, 505, 371 ], "spans": [ { "bbox": [ 89, 361, 505, 371 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 374, 465, 389 ], "spans": [ { "bbox": [ 88, 374, 465, 389 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 390, 504, 418 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 89, 391, 505, 403 ], "spans": [ { "bbox": [ 89, 391, 505, 403 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 407, 408, 419 ], "spans": [ { "bbox": [ 89, 407, 408, 419 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 422, 397, 434 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 89, 422, 398, 436 ], "spans": [ { "bbox": [ 89, 422, 398, 436 ], "type": "text", "content": "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：", "score": 1.0 } ] } ] }, { "bbox": [ 86, 453, 483, 481 ], "type": "list", "angle": 0, "index": 23, "blocks": [ { "bbox": [ 86, 453, 315, 465 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 454, 316, 467 ], "spans": [ { "bbox": [ 88, 454, 316, 467 ], "type": "text", "content": "(1)监督事务的执行，并测试是否违反完整性规则。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 468, 483, 481 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 469, 485, 482 ], "spans": [ { "bbox": [ 88, 469, 485, 482 ], "type": "text", "content": "(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。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 87, 484, 227, 497 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 89, 484, 227, 498 ], "spans": [ { "bbox": [ 89, 484, 227, 498 ], "type": "text", "content": "考核要求：达到“识记”层次", "score": 1.0 } ] } ] }, { "bbox": [ 87, 500, 236, 512 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 89, 501, 238, 513 ], "spans": [ { "bbox": [ 89, 501, 238, 513 ], "type": "text", "content": "知识点：规则的组成部分及分类", "score": 1.0 } ] } ] }, { "bbox": [ 86, 530, 338, 544 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 89, 531, 339, 544 ], "spans": [ { "bbox": [ 89, 531, 339, 544 ], "type": "text", "content": "数据库完整性子系统是根据“完整性规则集” 工作的，", "score": 1.0 } ] } ] }, { "bbox": [ 86, 546, 504, 575 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 89, 547, 505, 560 ], "spans": [ { "bbox": [ 89, 547, 505, 560 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 561, 119, 576 ], "spans": [ { "bbox": [ 88, 561, 119, 576 ], "type": "text", "content": "规则。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 593, 157, 605 ], "type": "title", "angle": 0, "index": 28, "lines": [ { "bbox": [ 88, 593, 159, 608 ], "spans": [ { "bbox": [ 88, 593, 159, 608 ], "type": "text", "content": "由三部分组成：", "score": 1.0 } ] } ] }, { "bbox": [ 94, 608, 246, 652 ], "type": "list", "angle": 0, "index": 32, "blocks": [ { "bbox": [ 94, 608, 246, 621 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 95, 608, 248, 623 ], "spans": [ { "bbox": [ 95, 608, 248, 623 ], "type": "text", "content": "（1）什么时候使用规则进行检查；", "score": 1.0 } ] } ] }, { "bbox": [ 94, 624, 215, 637 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 95, 623, 217, 639 ], "spans": [ { "bbox": [ 95, 623, 217, 639 ], "type": "text", "content": "（2）要检查什么样的错误；", "score": 1.0 } ] } ] }, { "bbox": [ 94, 640, 246, 652 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 95, 640, 247, 654 ], "spans": [ { "bbox": [ 95, 640, 247, 654 ], "type": "text", "content": "（3）若检查出错误，该怎样处理。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 86, 671, 304, 683 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 89, 671, 306, 684 ], "spans": [ { "bbox": [ 89, 671, 306, 684 ], "type": "text", "content": "在关系数据库中，这些完整性规则可分为三类：", "score": 1.0 } ] } ] }, { "bbox": [ 96, 687, 192, 730 ], "type": "list", "angle": 0, "index": 37, "blocks": [ { "bbox": [ 96, 687, 192, 699 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 97, 686, 193, 702 ], "spans": [ { "bbox": [ 97, 686, 193, 702 ], "type": "text", "content": "（1）用户定义完整性", "score": 1.0 } ] } ] }, { "bbox": [ 96, 702, 171, 714 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 97, 702, 172, 716 ], "spans": [ { "bbox": [ 97, 702, 172, 716 ], "type": "text", "content": "（2）实体完整性", "score": 1.0 } ] } ] }, { "bbox": [ 96, 718, 171, 730 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 97, 717, 172, 731 ], "spans": [ { "bbox": [ 97, 717, 172, 731 ], "type": "text", "content": "（3）参照完整性", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 87, 734, 309, 746 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 89, 734, 309, 748 ], "spans": [ { "bbox": [ 89, 734, 309, 748 ], "type": "text", "content": "1）主码约束：可用主码子句或主码短语来定义。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 750, 229, 761 ], "type": "text", "angle": 0, "index": 39, "lines": [ { "bbox": [ 88, 748, 231, 764 ], "spans": [ { "bbox": [ 88, 748, 231, 764 ], "type": "text", "content": "如 PRIMARY KEY (S#) (主码子句)", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 18 }, { "para_blocks": [ { "bbox": [ 94, 110, 263, 122 ], "type": "title", "angle": 0, "index": 1, "lines": [ { "bbox": [ 95, 110, 264, 124 ], "spans": [ { "bbox": [ 95, 110, 264, 124 ], "type": "text", "content": "（2）外码约束：可用外码子句来定义", "score": 1.0 } ] } ] }, { "bbox": [ 102, 126, 262, 138 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 102, 125, 263, 141 ], "spans": [ { "bbox": [ 102, 125, 263, 141 ], "type": "text", "content": "如 FOREIGN KEY (S#) REFERNCE S(S#)", "score": 1.0 } ] } ] }, { "type": "table", "bbox": [ 96, 138, 411, 224 ], "blocks": [ { "bbox": [ 96, 138, 411, 224 ], "lines": [ { "bbox": [ 96, 138, 411, 224 ], "spans": [ { "bbox": [ 96, 138, 411, 224 ], "type": "table", "html": "
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)
", "image_path": "03ea6d9dbbb50dbf2567c771b5c03ef056e50ba85a4f4bda59f5c8a5bdf29e22.jpg" } ] } ], "index": 3, "angle": 0, "type": "table_body" } ], "index": 3 }, { "bbox": [ 93, 226, 449, 254 ], "type": "list", "angle": 0, "index": 6, "blocks": [ { "bbox": [ 93, 226, 449, 239 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 94, 223, 451, 242 ], "spans": [ { "bbox": [ 94, 223, 451, 242 ], "type": "text", "content": "（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) ；", "score": 1.0 } ] } ] }, { "bbox": [ 94, 241, 319, 254 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 95, 239, 320, 258 ], "spans": [ { "bbox": [ 95, 239, 320, 258 ], "type": "text", "content": "（4）全局约束：包括基于元组的检查子句(CHECK)", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 88, 257, 462, 317 ], "type": "list", "angle": 0, "index": 11, "blocks": [ { "bbox": [ 88, 257, 462, 270 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 89, 256, 464, 272 ], "spans": [ { "bbox": [ 89, 258, 98, 269 ], "type": "inline_equation", "content": "\\star", "score": 0.66 }, { "bbox": [ 98, 256, 464, 272 ], "type": "text", "content": "在 employee 中插入记录，其 dno 值 not null， 但不在 department (dno) 中出现；", "score": 1.0 } ] } ] }, { "bbox": [ 89, 272, 452, 286 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 89, 271, 454, 288 ], "spans": [ { "bbox": [ 89, 274, 98, 285 ], "type": "inline_equation", "content": "\\star", "score": 0.8 }, { "bbox": [ 98, 271, 454, 288 ], "type": "text", "content": "修改 employee 的记录，新 dno 值 not null， 但不在 department (dno) 中出现；", "score": 1.0 } ] } ] }, { "bbox": [ 89, 288, 413, 301 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 89, 286, 415, 304 ], "spans": [ { "bbox": [ 89, 289, 98, 300 ], "type": "inline_equation", "content": "\\star", "score": 0.78 }, { "bbox": [ 99, 286, 415, 304 ], "type": "text", "content": "删除 department 的记录，但相应的 dno 值出现在 employee (dno) 中；", "score": 1.0 } ] } ] }, { "bbox": [ 89, 303, 413, 317 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 89, 302, 414, 319 ], "spans": [ { "bbox": [ 89, 305, 98, 316 ], "type": "inline_equation", "content": "\\star", "score": 0.71 }, { "bbox": [ 99, 302, 414, 319 ], "type": "text", "content": "修改 department 中的记录，但旧的 dno 值出现在 employee (dno) 中。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 87, 319, 283, 332 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 318, 285, 334 ], "spans": [ { "bbox": [ 88, 319, 181, 333 ], "type": "text", "content": "Restrict（限制策略）", "score": 1.0 }, { "bbox": [ 186, 318, 285, 334 ], "type": "text", "content": "——SQL 的默认策略，", "score": 1.0 } ] } ] }, { "bbox": [ 87, 334, 179, 348 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 334, 180, 350 ], "spans": [ { "bbox": [ 88, 334, 180, 350 ], "type": "text", "content": "针对以上四种情况；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 351, 98, 360 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 350, 100, 363 ], "spans": [ { "bbox": [ 89, 350, 100, 363 ], "type": "text", "content": "", "score": 1.0 } ] } ] }, { "bbox": [ 87, 365, 308, 379 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 364, 310, 381 ], "spans": [ { "bbox": [ 88, 364, 310, 381 ], "type": "text", "content": "Cascade（级联策略）——针对以上后两种情况；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 382, 98, 391 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 89, 381, 100, 393 ], "spans": [ { "bbox": [ 89, 381, 100, 393 ], "type": "text", "content": "", "score": 1.0 } ] } ] }, { "bbox": [ 87, 396, 307, 410 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 87, 396, 308, 412 ], "spans": [ { "bbox": [ 87, 396, 308, 412 ], "type": "text", "content": "Set Null（置空策略）——针对以上后两种情况。", "score": 1.0 } ] } ] }, { "bbox": [ 88, 412, 98, 422 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 89, 413, 99, 424 ], "spans": [ { "bbox": [ 89, 413, 99, 424 ], "type": "text", "content": "", "score": 1.0 } ] } ] }, { "bbox": [ 87, 428, 277, 441 ], "type": "title", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 427, 278, 444 ], "spans": [ { "bbox": [ 88, 427, 278, 444 ], "type": "text", "content": "三种策略有 On Delete , On Update 可供选", "score": 1.0 } ] } ] }, { "bbox": [ 87, 444, 237, 456 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 89, 444, 237, 456 ], "spans": [ { "bbox": [ 89, 444, 237, 456 ], "type": "text", "content": "对约束的命名、撤消和添加操作", "score": 1.0 } ] } ] }, { "bbox": [ 94, 460, 168, 472 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 95, 459, 169, 474 ], "spans": [ { "bbox": [ 95, 459, 169, 474 ], "type": "text", "content": "（1）约束的命名", "score": 1.0 } ] } ] }, { "bbox": [ 92, 475, 343, 487 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 94, 475, 344, 489 ], "spans": [ { "bbox": [ 94, 475, 344, 489 ], "type": "text", "content": "在定义时，前面加上关键字CONSTRACT和约束名即可。", "score": 1.0 } ] } ] }, { "bbox": [ 94, 491, 242, 503 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 95, 491, 242, 504 ], "spans": [ { "bbox": [ 95, 491, 242, 504 ], "type": "text", "content": "（2）在关系上约束的撤消与添加", "score": 1.0 } ] } ] }, { "bbox": [ 94, 506, 504, 534 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 96, 506, 506, 520 ], "spans": [ { "bbox": [ 96, 506, 506, 520 ], "type": "text", "content": "在 关 系 定义中 ，撤消约 束 用 “ALTER TABLE ...DROP CONSTRAINT...”语 句 ，添加约 束 用", "score": 1.0 } ] }, { "bbox": [ 94, 522, 277, 535 ], "spans": [ { "bbox": [ 94, 522, 277, 535 ], "type": "text", "content": "“ALTER TABLE ...ADD CONSTRAINT ...”语句", "score": 1.0 } ] } ] }, { "bbox": [ 88, 537, 153, 550 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 88, 536, 156, 550 ], "spans": [ { "bbox": [ 88, 536, 156, 550 ], "type": "text", "content": " Check 约束：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 553, 294, 565 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 89, 551, 296, 568 ], "spans": [ { "bbox": [ 89, 554, 98, 565 ], "type": "inline_equation", "content": "\\star", "score": 0.54 }, { "bbox": [ 99, 551, 296, 568 ], "type": "text", "content": "约束条件可以是任何 Where 中出现的字句；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 568, 199, 581 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 567, 201, 582 ], "spans": [ { "bbox": [ 88, 567, 201, 582 ], "type": "text", "content": "故具有很强的表述能力；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 584, 209, 597 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 89, 583, 210, 597 ], "spans": [ { "bbox": [ 89, 585, 98, 596 ], "type": "inline_equation", "content": "\\star", "score": 0.58 }, { "bbox": [ 99, 583, 210, 597 ], "type": "text", "content": "常用于数据的值域约束；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 601, 293, 613 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 88, 599, 294, 615 ], "spans": [ { "bbox": [ 88, 599, 294, 615 ], "type": "text", "content": "三、User Defined Integrity and Default、Check", "score": 1.0 } ] } ] }, { "bbox": [ 88, 616, 170, 628 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 88, 615, 171, 629 ], "spans": [ { "bbox": [ 88, 615, 171, 629 ], "type": "text", "content": "Col_constr 列约束", "score": 1.0 } ] } ] }, { "bbox": [ 88, 630, 287, 644 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 89, 630, 287, 645 ], "spans": [ { "bbox": [ 89, 630, 287, 645 ], "type": "text", "content": "一种域约束类型，对单一列的值进行约束", "score": 1.0 } ] } ] }, { "bbox": [ 88, 646, 146, 658 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 88, 646, 148, 661 ], "spans": [ { "bbox": [ 88, 646, 148, 661 ], "type": "text", "content": "{ NOT NULL |", "score": 1.0 } ] } ] }, { "bbox": [ 88, 661, 229, 674 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 87, 661, 231, 677 ], "spans": [ { "bbox": [ 87, 661, 231, 677 ], "type": "text", "content": "[ CONSTRAINT constraintname ]", "score": 1.0 } ] } ] }, { "bbox": [ 88, 677, 132, 689 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 86, 677, 133, 692 ], "spans": [ { "bbox": [ 86, 677, 133, 692 ], "type": "text", "content": "{ UNIQUE", "score": 1.0 } ] } ] }, { "bbox": [ 88, 693, 157, 704 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 88, 692, 158, 707 ], "spans": [ { "bbox": [ 88, 692, 158, 707 ], "type": "text", "content": "| PRIMARY KEY", "score": 1.0 } ] } ] }, { "bbox": [ 89, 708, 126, 720 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 88, 708, 128, 723 ], "spans": [ { "bbox": [ 88, 708, 128, 723 ], "type": "text", "content": "| CHECK", "score": 1.0 } ] } ] }, { "bbox": [ 88, 724, 151, 736 ], "type": "text", "angle": 0, "index": 37, "lines": [ { "bbox": [ 88, 724, 153, 739 ], "spans": [ { "bbox": [ 88, 724, 153, 739 ], "type": "text", "content": "(search_cond)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 740, 140, 752 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 88, 740, 141, 754 ], "spans": [ { "bbox": [ 88, 740, 141, 754 ], "type": "text", "content": "//列值非空", "score": 1.0 } ] } ] } ], "discarded_blocks": [ { "bbox": [ 87, 79, 354, 92 ], "type": "header", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 78, 354, 94 ], "spans": [ { "bbox": [ 88, 78, 354, 94 ], "type": "text", "content": "S# CHAR (4) PRIMARY KEY (其中，PRIMARY KEY 为主码短语）", "score": 1.0 } ] } ] } ], "page_size": [ 595, 841 ], "page_idx": 19 }, { "para_blocks": [ { "bbox": [ 86, 79, 224, 91 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 89, 79, 224, 92 ], "spans": [ { "bbox": [ 89, 79, 224, 92 ], "type": "text", "content": "//为约束命名，便于以后撤消", "score": 1.0 } ] } ] }, { "bbox": [ 87, 95, 151, 106 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 95, 152, 108 ], "spans": [ { "bbox": [ 88, 95, 152, 108 ], "type": "text", "content": "//列值是唯一", "score": 1.0 } ] } ] }, { "bbox": [ 87, 110, 141, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 111, 141, 124 ], "spans": [ { "bbox": [ 88, 111, 141, 124 ], "type": "text", "content": "//列为主键", "score": 1.0 } ] } ] }, { "bbox": [ 86, 125, 258, 138 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 126, 258, 139 ], "spans": [ { "bbox": [ 88, 126, 258, 139 ], "type": "text", "content": "//列值满足条件,条件只能使用列当前", "score": 1.0 } ] } ] }, { "bbox": [ 87, 142, 101, 153 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 141, 102, 156 ], "spans": [ { "bbox": [ 88, 141, 102, 156 ], "type": "text", "content": "值", "score": 1.0 } ] } ] }, { "bbox": [ 88, 156, 256, 169 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 88, 155, 258, 171 ], "spans": [ { "bbox": [ 88, 155, 258, 171 ], "type": "text", "content": "| REFERENCES tablename [(colname) ]", "score": 1.0 } ] } ] }, { "bbox": [ 88, 172, 252, 185 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 88, 171, 254, 188 ], "spans": [ { "bbox": [ 88, 171, 254, 188 ], "type": "text", "content": "[ON DELETE { CASCADE | SET NULL } ]", "score": 1.0 } ] } ] }, { "bbox": [ 88, 188, 99, 200 ], "type": "text", "angle": 0, "index": 7, "lines": [] }, { "bbox": [ 86, 203, 446, 248 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 88, 203, 436, 217 ], "spans": [ { "bbox": [ 88, 203, 436, 217 ], "type": "text", "content": "//引用另一表 tablename 的列 colname 的值，如有 ON DELETE CASCADE 或 ON", "score": 1.0 } ] }, { "bbox": [ 88, 219, 447, 233 ], "spans": [ { "bbox": [ 88, 219, 426, 233 ], "type": "text", "content": "DELETE 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", "score": 1.0 }, { "bbox": [ 427, 221, 434, 232 ], "type": "inline_equation", "content": "\\mathsf { v }", "score": 0.66 }, { "bbox": [ 435, 219, 447, 233 ], "type": "text", "content": "的", "score": 1.0 } ] }, { "bbox": [ 88, 235, 295, 248 ], "spans": [ { "bbox": [ 88, 235, 295, 248 ], "type": "text", "content": "记录删除或列值更新为 null；缺省为无操作 。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 250, 370, 263 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 249, 370, 265 ], "spans": [ { "bbox": [ 88, 249, 370, 265 ], "type": "text", "content": " Col_constr 列约束：只能应用在单一列上，其后面的约束如", "score": 1.0 } ] } ] }, { "bbox": [ 86, 266, 351, 279 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 266, 351, 281 ], "spans": [ { "bbox": [ 88, 266, 351, 281 ], "type": "text", "content": "UNIQUE, PRIMARY KEY 及 search_cond 只能是单一列唯一、", "score": 1.0 } ] } ] }, { "bbox": [ 87, 281, 206, 294 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 89, 281, 207, 295 ], "spans": [ { "bbox": [ 89, 281, 207, 295 ], "type": "text", "content": "单一列为主键、和单一列", "score": 1.0 } ] } ] }, { "bbox": [ 88, 297, 111, 309 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 86, 296, 113, 313 ], "spans": [ { "bbox": [ 86, 296, 113, 313 ], "type": "text", "content": "相关", "score": 1.0 } ] } ] }, { "bbox": [ 93, 317, 193, 333 ], "type": "title", "angle": 0, "index": 13, "lines": [ { "bbox": [ 92, 316, 195, 333 ], "spans": [ { "bbox": [ 92, 316, 195, 333 ], "type": "text", "content": "Col_constr列约束", "score": 0.993 } ] } ] }, { "bbox": [ 93, 336, 262, 348 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 92, 335, 262, 349 ], "spans": [ { "bbox": [ 92, 335, 262, 349 ], "type": "text", "content": "》一种域约束类型，对单一列的值进行约束", "score": 0.978 } ] } ] }, { "bbox": [ 93, 349, 151, 361 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 92, 348, 152, 363 ], "spans": [ { "bbox": [ 92, 348, 152, 363 ], "type": "text", "content": "{ NOT NULL |", "score": 0.867 } ] } ] }, { "bbox": [ 281, 349, 314, 359 ], "type": "text", "angle": 0, "index": 16, "lines": [] }, { "bbox": [ 94, 363, 232, 375 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 93, 361, 233, 376 ], "spans": [ { "bbox": [ 93, 361, 233, 376 ], "type": "text", "content": "[ CONSTRAINT constraintname ]", "score": 0.98 } ] } ] }, { "bbox": [ 281, 363, 367, 372 ], "type": "text", "angle": 0, "index": 18, "lines": [] }, { "bbox": [ 94, 377, 139, 387 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 92, 375, 140, 388 ], "spans": [ { "bbox": [ 92, 375, 140, 388 ], "type": "text", "content": "{UNIQUE", "score": 0.975 } ] } ] }, { "bbox": [ 281, 377, 321, 386 ], "type": "text", "angle": 0, "index": 20, "lines": [] }, { "bbox": [ 94, 391, 161, 401 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 92, 389, 163, 401 ], "spans": [ { "bbox": [ 92, 389, 163, 401 ], "type": "text", "content": "PRIMARY KEY", "score": 0.971 } ] } ] }, { "bbox": [ 281, 390, 314, 398 ], "type": "text", "angle": 0, "index": 22, "lines": [] }, { "bbox": [ 94, 404, 132, 415 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 91, 402, 134, 416 ], "spans": [ { "bbox": [ 91, 402, 134, 416 ], "type": "text", "content": "|CHECK", "score": 0.947 } ] } ] }, { "bbox": [ 165, 405, 227, 416 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 165, 403, 228, 417 ], "spans": [ { "bbox": [ 165, 403, 228, 417 ], "type": "text", "content": "(search_cond)", "score": 1.0 } ] } ] }, { "bbox": [ 281, 403, 389, 412 ], "type": "text", "angle": 0, "index": 25, "lines": [] }, { "bbox": [ 281, 412, 288, 418 ], "type": "text", "angle": 0, "index": 26, "lines": [] }, { "bbox": [ 155, 418, 332, 430 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 152, 414, 334, 432 ], "spans": [ { "bbox": [ 152, 414, 334, 432 ], "type": "text", "content": "| REFERENCES tablename [(colname)]", "score": 0.959 } ] } ] }, { "bbox": [ 349, 431, 362, 443 ], "type": "text", "angle": 0, "index": 28, "lines": [] }, { "bbox": [ 155, 432, 362, 444 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 154, 429, 324, 445 ], "spans": [ { "bbox": [ 154, 429, 324, 445 ], "type": "text", "content": "[ON DELETE{CASCADE| SET NULL}]", "score": 0.95 } ] } ] }, { "bbox": [ 154, 444, 399, 473 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 155, 444, 400, 452 ], "spans": [ { "bbox": [ 155, 444, 400, 452 ], "type": "text", "content": "//引用另一表tablename的列colname的值，如有ONDELETECASCADE或ON", "score": 0.991 } ] }, { "bbox": [ 155, 454, 399, 462 ], "spans": [ { "bbox": [ 155, 454, 399, 462 ], "type": "text", "content": "DELETESETNULL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", "score": 0.977 } ] }, { "bbox": [ 155, 465, 290, 472 ], "spans": [ { "bbox": [ 155, 465, 290, 472 ], "type": "text", "content": "记录删除或列值更新为null：缺省为无操作。", "score": 0.973 } ] } ] }, { "bbox": [ 154, 474, 397, 508 ], "type": "text", "angle": 0, "index": 31, "lines": [ { "bbox": [ 154, 474, 398, 486 ], "spans": [ { "bbox": [ 154, 475, 164, 485 ], "type": "inline_equation", "content": "\\gtrdot", "score": 0.52 }, { "bbox": [ 164, 474, 398, 486 ], "type": "text", "content": "Col_constr列约束：只能应用在单一列上，其后面的约束如", "score": 0.997 } ] }, { "bbox": [ 155, 486, 395, 497 ], "spans": [ { "bbox": [ 155, 486, 395, 497 ], "type": "text", "content": "UNIQUE，PRIMARYKEY及search_cond只能是单一列唯一、", "score": 0.959 } ] }, { "bbox": [ 155, 497, 254, 508 ], "spans": [ { "bbox": [ 155, 497, 254, 508 ], "type": "text", "content": "单一列为主键、和单一列", "score": 1.0 } ] } ] }, { "bbox": [ 155, 510, 174, 521 ], "type": "text", "angle": 0, "index": 32, "lines": [ { "bbox": [ 154, 509, 176, 523 ], "spans": [ { "bbox": [ 154, 509, 176, 523 ], "type": "text", "content": "相关", "score": 1.0 } ] } ] }, { "bbox": [ 97, 547, 143, 556 ], "type": "text", "angle": 0, "index": 33, "lines": [ { "bbox": [ 95, 545, 145, 558 ], "spans": [ { "bbox": [ 95, 545, 145, 558 ], "type": "text", "content": "Create Table", "score": 0.986 } ] } ] }, { "bbox": [ 165, 548, 208, 556 ], "type": "text", "angle": 0, "index": 34, "lines": [ { "bbox": [ 164, 546, 210, 558 ], "spans": [ { "bbox": [ 164, 546, 210, 558 ], "type": "text", "content": "Student (S#", "score": 0.996 } ] } ] }, { "bbox": [ 233, 548, 342, 556 ], "type": "text", "angle": 0, "index": 35, "lines": [ { "bbox": [ 233, 547, 343, 558 ], "spans": [ { "bbox": [ 233, 547, 343, 558 ], "type": "text", "content": "char(8) not null unique, Sname", "score": 0.984 } ] } ] }, { "bbox": [ 97, 559, 357, 568 ], "type": "text", "angle": 0, "index": 36, "lines": [ { "bbox": [ 95, 557, 358, 569 ], "spans": [ { "bbox": [ 95, 557, 358, 569 ], "type": "text", "content": "char(10), Ssex char(2) constraint ctssex check (Ssex= ‘男’or Ssex=‘女", "score": 0.969 } ] } ] }, { "bbox": [ 97, 570, 111, 579 ], "type": "text", "angle": 0, "index": 37, "lines": [] }, { "bbox": [ 131, 570, 302, 579 ], "type": "text", "angle": 0, "index": 38, "lines": [ { "bbox": [ 130, 568, 303, 580 ], "spans": [ { "bbox": [ 130, 568, 303, 580 ], "type": "text", "content": " Sage integer check (Sage>=1 and Sage<150), D#", "score": 0.966 } ] } ] }, { "bbox": [ 131, 581, 295, 590 ], "type": "text", "angle": 0, "index": 39, "lines": [ { "bbox": [ 130, 579, 296, 591 ], "spans": [ { "bbox": [ 130, 579, 296, 591 ], "type": "text", "content": "char(2) references Dept(D#) on delete cascade,", "score": 0.988 } ] } ] }, { "bbox": [ 97, 593, 155, 602 ], "type": "text", "angle": 0, "index": 40, "lines": [ { "bbox": [ 96, 591, 158, 604 ], "spans": [ { "bbox": [ 96, 591, 158, 604 ], "type": "text", "content": " Sclass char(6) );", "score": 0.95 } ] } ] }, { "bbox": [ 97, 602, 245, 612 ], "type": "text", "angle": 0, "index": 41, "lines": [ { "bbox": [ 97, 602, 246, 612 ], "spans": [ { "bbox": [ 97, 602, 246, 612 ], "type": "text", "content": "//假定Ssex只能取{男，女},1==0.0 and", "score": 0.983 } ] } ] }, { "bbox": [ 164, 665, 396, 677 ], "type": "text", "angle": 0, "index": 45, "lines": [ { "bbox": [ 163, 665, 398, 676 ], "spans": [ { "bbox": [ 163, 665, 398, 676 ], "type": "text", "content": "Credit<=5.0).T# char(3) references Teacher(T#) on delete", "score": 0.972 } ] } ] }, { "bbox": [ 164, 679, 207, 689 ], "type": "text", "angle": 0, "index": 46, "lines": [ { "bbox": [ 163, 677, 208, 691 ], "spans": [ { "bbox": [ 163, 677, 208, 691 ], "type": "text", "content": "cascade);", "score": 0.99 } ] } ] }, { "bbox": [ 164, 692, 261, 700 ], "type": "text", "angle": 0, "index": 47, "lines": [] }, { "bbox": [ 164, 701, 176, 708 ], "type": "text", "angle": 0, "index": 48, "lines": [] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 20 }, { "para_blocks": [ { "bbox": [ 98, 83, 450, 101 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 95, 80, 451, 103 ], "spans": [ { "bbox": [ 95, 80, 451, 103 ], "type": "text", "content": "》一种关系约束类型，对多列或元组的值进行约束", "score": 0.978 } ] } ] }, { "type": "code", "bbox": [ 126, 106, 595, 294 ], "blocks": [ { "bbox": [ 126, 106, 595, 294 ], "lines": [ { "bbox": [ 126, 106, 595, 294 ], "spans": [ { "bbox": [ 126, 106, 595, 294 ], "type": "text", "content": "[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]" } ] } ], "index": 1, "angle": 0, "type": "code_body" } ], "index": 1, "sub_type": "code", "guess_lang": "txt" }, { "bbox": [ 154, 299, 404, 314 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 155, 300, 403, 315 ], "spans": [ { "bbox": [ 155, 300, 403, 315 ], "type": "text", "content": "引用另一表tablename的若干列的值作为外键", "score": 0.999 } ] } ] }, { "bbox": [ 154, 317, 595, 359 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 157, 316, 595, 336 ], "spans": [ { "bbox": [ 157, 316, 595, 336 ], "type": "text", "content": ">table_constr表约束：是应用在关系上，即对关系的多列或", "score": 0.988 } ] }, { "bbox": [ 155, 338, 343, 359 ], "spans": [ { "bbox": [ 155, 338, 343, 359 ], "type": "text", "content": "行约束，列约束是其特例", "score": 0.999 } ] } ] }, { "type": "code", "bbox": [ 99, 421, 377, 489 ], "blocks": [ { "bbox": [ 99, 421, 377, 489 ], "lines": [ { "bbox": [ 99, 421, 377, 489 ], "spans": [ { "bbox": [ 99, 421, 377, 489 ], "type": "text", "content": "Create 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#));" } ] } ], "index": 4, "angle": 0, "type": "code_body" } ], "index": 4, "sub_type": "code", "guess_lang": "sql" }, { "type": "code", "bbox": [ 117, 493, 379, 562 ], "blocks": [ { "bbox": [ 117, 493, 379, 562 ], "lines": [ { "bbox": [ 117, 493, 379, 562 ], "spans": [ { "bbox": [ 117, 493, 379, 562 ], "type": "text", "content": "Create 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));" } ] } ], "index": 5, "angle": 0, "type": "code_body" } ], "index": 5, "sub_type": "code", "guess_lang": "txt" }, { "type": "code", "bbox": [ 152, 564, 244, 573 ], "blocks": [ { "bbox": [ 152, 564, 244, 573 ], "lines": [ { "bbox": [ 152, 564, 244, 573 ], "spans": [ { "bbox": [ 152, 564, 244, 573 ], "type": "text", "content": "//假定严格约束20学时一个学分" } ] } ], "index": 6, "angle": 0, "type": "code_body" } ], "index": 6, "sub_type": "code", "guess_lang": "txt" } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 21 }, { "para_blocks": [ { "bbox": [ 149, 74, 345, 94 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 147, 74, 344, 96 ], "spans": [ { "bbox": [ 147, 74, 344, 96 ], "type": "text", "content": "4.1.4约米的修改", "score": 0.895 } ] } ] }, { "bbox": [ 97, 111, 517, 137 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 94, 107, 515, 139 ], "spans": [ { "bbox": [ 94, 107, 515, 139 ], "type": "text", "content": "■先给约束命名，然后进行增加或者删除。", "score": 0.997 } ] } ] }, { "bbox": [ 96, 143, 564, 204 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 126, 141, 562, 171 ], "spans": [ { "bbox": [ 126, 141, 211, 171 ], "type": "text", "content": "★命名：", "score": 0.973 }, { "bbox": [ 239, 142, 562, 170 ], "type": "text", "content": "Constraint<约束名><约束定义>", "score": 0.994 } ] }, { "bbox": [ 95, 177, 130, 205 ], "spans": [ { "bbox": [ 95, 177, 130, 205 ], "type": "text", "content": "Eg.", "score": 0.994 } ] } ] }, { "bbox": [ 120, 210, 595, 353 ], "type": "list", "angle": 0, "index": 6, "blocks": [ { "bbox": [ 122, 210, 464, 235 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 168, 203, 468, 241 ], "spans": [ { "bbox": [ 168, 203, 468, 241 ], "type": "text", "content": " eno char(2) constraint pk_emp,", "score": 0.993 } ] } ] }, { "bbox": [ 120, 243, 595, 294 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 120, 240, 595, 268 ], "spans": [ { "bbox": [ 120, 243, 147, 267 ], "type": "text", "content": "2.", "score": 0.98 }, { "bbox": [ 172, 240, 595, 268 ], "type": "text", "content": " sex char(2) constraint chk_sex check (sex IN", "score": 0.975 } ] } ] }, { "bbox": [ 121, 301, 595, 353 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 119, 298, 595, 329 ], "spans": [ { "bbox": [ 119, 298, 459, 329 ], "type": "text", "content": "3. Constraint chk_namesex check(", "score": 0.974 }, { "bbox": [ 460, 301, 543, 326 ], "type": "inline_equation", "content": "\\mathrm { s e x } = \\mathrm { \\tilde { F } } \\mathrm { \\tilde { \\Omega } }", "score": 0.51 }, { "bbox": [ 543, 298, 595, 329 ], "type": "text", "content": "or na", "score": 0.901 } ] }, { "bbox": [ 162, 327, 325, 354 ], "spans": [ { "bbox": [ 162, 327, 325, 354 ], "type": "text", "content": "not like‘Ms.%)", "score": 0.975 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 131, 360, 452, 386 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 130, 355, 452, 389 ], "spans": [ { "bbox": [ 130, 355, 452, 389 ], "type": "text", "content": "★增加：alter table ", "score": 0.996 } ] } ] }, { "bbox": [ 230, 391, 595, 417 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 227, 389, 595, 420 ], "spans": [ { "bbox": [ 227, 389, 595, 420 ], "type": "text", "content": "Add Constraint<约束名><约束定义>", "score": 0.974 } ] } ] }, { "bbox": [ 132, 424, 452, 451 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 130, 420, 452, 454 ], "spans": [ { "bbox": [ 130, 420, 452, 454 ], "type": "text", "content": "★删除：alter table ", "score": 0.979 } ] } ] }, { "bbox": [ 303, 457, 552, 483 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 302, 453, 555, 486 ], "spans": [ { "bbox": [ 302, 453, 555, 486 ], "type": "text", "content": "drop Constraint <约束名>", "score": 0.982 } ] } ] }, { "bbox": [ 86, 576, 206, 590 ], "type": "title", "angle": 0, "index": 11, "lines": [ { "bbox": [ 89, 578, 205, 590 ], "spans": [ { "bbox": [ 89, 578, 205, 590 ], "type": "text", "content": "是拒绝、级联删除、置空", "score": 1.0 } ] } ] }, { "bbox": [ 87, 592, 185, 606 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 592, 185, 608 ], "spans": [ { "bbox": [ 88, 592, 185, 608 ], "type": "text", "content": "1. 属性（列）级约束", "score": 1.0 } ] } ] }, { "bbox": [ 104, 608, 171, 620 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 107, 608, 171, 622 ], "spans": [ { "bbox": [ 107, 613, 111, 616 ], "type": "text", "content": "", "score": 0.0 }, { "bbox": [ 123, 608, 171, 622 ], "type": "text", "content": "NOT NULL", "score": 1.0 } ] } ] }, { "bbox": [ 122, 624, 294, 637 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 123, 622, 297, 640 ], "spans": [ { "bbox": [ 123, 622, 297, 640 ], "type": "text", "content": "禁止该列出现 NULL 值（必须填写）。", "score": 1.0 } ] } ] }, { "bbox": [ 104, 640, 163, 651 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 107, 640, 164, 653 ], "spans": [ { "bbox": [ 107, 644, 112, 648 ], "type": "text", "content": ".", "score": 0.706 }, { "bbox": [ 122, 640, 164, 653 ], "type": "text", "content": "UNIQUE", "score": 1.0 } ] } ] }, { "bbox": [ 122, 655, 504, 684 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 124, 655, 505, 668 ], "spans": [ { "bbox": [ 124, 655, 505, 668 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 123, 670, 155, 686 ], "spans": [ { "bbox": [ 123, 670, 155, 686 ], "type": "text", "content": "现）。", "score": 1.0 } ] } ] }, { "bbox": [ 105, 687, 155, 698 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 123, 687, 156, 700 ], "spans": [ { "bbox": [ 123, 687, 156, 700 ], "type": "text", "content": "CHECK", "score": 1.0 } ] } ] }, { "bbox": [ 122, 702, 327, 715 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 124, 701, 327, 718 ], "spans": [ { "bbox": [ 124, 701, 293, 718 ], "type": "text", "content": "定义列值的检查条件，如 CHECK (age", "score": 1.0 }, { "bbox": [ 293, 703, 319, 714 ], "type": "inline_equation", "content": "\\bf { \\sigma } > 1 8", "score": 0.67 }, { "bbox": [ 320, 701, 327, 718 ], "type": "text", "content": ")。", "score": 1.0 } ] } ] }, { "bbox": [ 105, 718, 164, 729 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 123, 719, 165, 730 ], "spans": [ { "bbox": [ 123, 719, 165, 730 ], "type": "text", "content": "DEFAULT", "score": 1.0 } ] } ] }, { "bbox": [ 122, 733, 292, 746 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 124, 733, 293, 749 ], "spans": [ { "bbox": [ 124, 733, 293, 749 ], "type": "text", "content": "设置默认值，如 DEFAULT 'unknown'。", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 22 }, { "para_blocks": [ { "bbox": [ 86, 79, 185, 92 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 79, 185, 92 ], "spans": [ { "bbox": [ 88, 79, 185, 92 ], "type": "text", "content": "2. 表（外键）级约束", "score": 1.0 } ] } ] }, { "bbox": [ 86, 94, 505, 123 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 89, 95, 505, 109 ], "spans": [ { "bbox": [ 89, 95, 505, 109 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 109, 327, 124 ], "spans": [ { "bbox": [ 88, 109, 327, 124 ], "type": "text", "content": "更新或删除时，子表（引用表）如何处理相关记录：", "score": 1.0 } ] } ] }, { "type": "table", "bbox": [ 86, 132, 512, 388 ], "blocks": [ { "bbox": [ 86, 132, 512, 388 ], "lines": [ { "bbox": [ 86, 132, 512, 388 ], "spans": [ { "bbox": [ 86, 132, 512, 388 ], "type": "table", "html": "
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）。
", "image_path": "2744a311ec2af69639b0916157b35c690cab9b256662f68668e640ab247e3059.jpg" } ] } ], "index": 2, "angle": 0, "type": "table_body" } ], "index": 2 }, { "bbox": [ 87, 406, 154, 418 ], "type": "title", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 405, 155, 419 ], "spans": [ { "bbox": [ 88, 405, 155, 419 ], "type": "text", "content": " Check 约束：", "score": 1.0 } ] } ] }, { "bbox": [ 88, 421, 295, 465 ], "type": "list", "angle": 0, "index": 7, "blocks": [ { "bbox": [ 88, 421, 295, 433 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 89, 419, 296, 436 ], "spans": [ { "bbox": [ 89, 422, 98, 433 ], "type": "inline_equation", "content": "\\star", "score": 0.67 }, { "bbox": [ 99, 419, 296, 436 ], "type": "text", "content": "约束条件可以是任何 Where 中出现的字句；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 437, 201, 449 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 88, 436, 201, 451 ], "spans": [ { "bbox": [ 88, 436, 201, 451 ], "type": "text", "content": "故具有很强的表述能力；", "score": 1.0 } ] } ] }, { "bbox": [ 89, 453, 210, 465 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 89, 453, 210, 466 ], "spans": [ { "bbox": [ 89, 453, 98, 464 ], "type": "inline_equation", "content": "\\star", "score": 0.68 }, { "bbox": [ 99, 453, 210, 466 ], "type": "text", "content": "常用于数据的值域约束；", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 88, 469, 294, 481 ], "type": "title", "angle": 0, "index": 8, "lines": [ { "bbox": [ 89, 467, 295, 483 ], "spans": [ { "bbox": [ 89, 467, 295, 483 ], "type": "text", "content": "三、User Defined Integrity and Default、Check", "score": 1.0 } ] } ] }, { "bbox": [ 88, 484, 103, 496 ], "type": "title", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 483, 107, 500 ], "spans": [ { "bbox": [ 88, 483, 107, 500 ], "type": "text", "content": "Eg.", "score": 1.0 } ] } ] }, { "bbox": [ 88, 498, 333, 528 ], "type": "list", "angle": 0, "index": 12, "blocks": [ { "bbox": [ 88, 498, 333, 512 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 86, 496, 336, 516 ], "spans": [ { "bbox": [ 86, 496, 336, 516 ], "type": "text", "content": "1. sex char(2) check (sex IN (‘男’,‘女’)) default‘男 ’，", "score": 1.0 } ] } ] }, { "bbox": [ 88, 515, 267, 528 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 88, 515, 268, 530 ], "spans": [ { "bbox": [ 88, 515, 235, 530 ], "type": "text", "content": "2. age int check (age>=16 and age", "score": 1.0 }, { "bbox": [ 235, 516, 257, 527 ], "type": "inline_equation", "content": "\\mathtt { < } \\mathtt { = } 7 0", "score": 0.71 }, { "bbox": [ 257, 515, 268, 530 ], "type": "text", "content": ")，", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 88, 531, 103, 542 ], "type": "title", "angle": 0, "index": 13, "lines": [ { "bbox": [ 88, 529, 107, 546 ], "spans": [ { "bbox": [ 88, 529, 107, 546 ], "type": "text", "content": "Eg.", "score": 1.0 } ] } ] }, { "bbox": [ 88, 545, 333, 575 ], "type": "list", "angle": 0, "index": 16, "blocks": [ { "bbox": [ 88, 545, 333, 560 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 86, 542, 336, 563 ], "spans": [ { "bbox": [ 86, 542, 336, 563 ], "type": "text", "content": "1. sex char(2) check (sex IN (‘男’,‘女’)) default‘男 ’，", "score": 1.0 } ] } ] }, { "bbox": [ 88, 562, 267, 575 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 86, 560, 269, 577 ], "spans": [ { "bbox": [ 86, 560, 235, 577 ], "type": "text", "content": "2. age int check (age>=16 and age", "score": 1.0 }, { "bbox": [ 235, 563, 257, 574 ], "type": "inline_equation", "content": "\\mathtt { < } \\mathtt { = } 7 0", "score": 0.78 }, { "bbox": [ 258, 560, 269, 577 ], "type": "text", "content": ")，", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 88, 592, 154, 606 ], "type": "title", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 591, 155, 608 ], "spans": [ { "bbox": [ 88, 591, 155, 608 ], "type": "text", "content": "触发器 Trigger", "score": 1.0 } ] } ] }, { "bbox": [ 87, 608, 411, 699 ], "type": "list", "angle": 0, "index": 20, "blocks": [ { "bbox": [ 87, 608, 411, 652 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 88, 608, 408, 622 ], "spans": [ { "bbox": [ 88, 608, 408, 622 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 624, 412, 638 ], "spans": [ { "bbox": [ 88, 624, 412, 638 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 639, 365, 655 ], "spans": [ { "bbox": [ 88, 639, 365, 655 ], "type": "text", "content": "以及多个元组之间的完整性约束，就需要触发器技术 Trigger", "score": 1.0 } ] } ] }, { "bbox": [ 88, 655, 411, 699 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 655, 410, 669 ], "spans": [ { "bbox": [ 88, 655, 410, 669 ], "type": "text", "content": "Trigger是一种过程完整性约束(相⽐之下，Create Table中定义的都是", "score": 1.0 } ] }, { "bbox": [ 88, 671, 401, 685 ], "spans": [ { "bbox": [ 88, 671, 401, 685 ], "type": "text", "content": "非过程性约束),是一段 SQL 程序，该程序在对表或视图执行 UPDATE、", "score": 1.0 } ] }, { "bbox": [ 88, 687, 268, 699 ], "spans": [ { "bbox": [ 88, 687, 268, 699 ], "type": "text", "content": "INSERT 或 DELETE 操作时自动触发执行。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 88, 702, 141, 714 ], "type": "title", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 701, 141, 716 ], "spans": [ { "bbox": [ 88, 701, 141, 716 ], "type": "text", "content": "基本语法", "score": 1.0 } ] } ] }, { "bbox": [ 88, 718, 161, 729 ], "type": "title", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 718, 162, 731 ], "spans": [ { "bbox": [ 88, 718, 162, 731 ], "type": "text", "content": "CREATETRIGGER", "score": 1.0 } ] } ] }, { "bbox": [ 88, 733, 149, 745 ], "type": "title", "angle": 0, "index": 23, "lines": [ { "bbox": [ 87, 732, 151, 747 ], "spans": [ { "bbox": [ 87, 732, 151, 747 ], "type": "text", "content": "trigger_name", "score": 1.0 } ] } ] }, { "bbox": [ 88, 749, 161, 760 ], "type": "title", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 749, 162, 761 ], "spans": [ { "bbox": [ 88, 749, 162, 761 ], "type": "text", "content": "BEFORE | AFTER", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 23 }, { "para_blocks": [ { "type": "code", "bbox": [ 86, 79, 385, 122 ], "blocks": [ { "bbox": [ 86, 79, 385, 122 ], "lines": [ { "bbox": [ 86, 79, 385, 122 ], "spans": [ { "bbox": [ 86, 79, 385, 122 ], "type": "text", "content": "{ INSERT | DELETE | UPDATE [OF colname {, colname...}] } ON tablename [REFERENCING corr_name_def {, corr_name_def...}] [FOR EACH ROW | FOR EACH STATEMENT]" } ] } ], "index": 0, "angle": 0, "type": "code_body" } ], "index": 0, "sub_type": "code", "guess_lang": "sql" }, { "bbox": [ 86, 125, 503, 138 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 87, 125, 502, 139 ], "spans": [ { "bbox": [ 87, 125, 502, 139 ], "type": "text", "content": "//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)", "score": 1.0 } ] } ] }, { "type": "code", "bbox": [ 87, 141, 210, 168 ], "blocks": [ { "bbox": [ 87, 141, 210, 168 ], "lines": [ { "bbox": [ 87, 141, 210, 168 ], "spans": [ { "bbox": [ 87, 141, 210, 168 ], "type": "text", "content": "[WHEN (search_condition)] { statement" } ] } ], "index": 2, "angle": 0, "type": "code_body" } ], "index": 2, "sub_type": "code", "guess_lang": "objectivec" }, { "bbox": [ 86, 172, 246, 185 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 89, 174, 245, 185 ], "spans": [ { "bbox": [ 89, 174, 245, 185 ], "type": "text", "content": "//检查条件，如满足执行下述程序", "score": 1.0 } ] } ] }, { "bbox": [ 86, 188, 298, 200 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 188, 298, 201 ], "spans": [ { "bbox": [ 88, 188, 298, 201 ], "type": "text", "content": "//单行程序直接书写，多行程序要用下行方式", "score": 1.0 } ] } ] }, { "type": "code", "bbox": [ 88, 203, 307, 216 ], "blocks": [ { "bbox": [ 88, 203, 307, 216 ], "lines": [ { "bbox": [ 88, 203, 307, 216 ], "spans": [ { "bbox": [ 88, 203, 307, 216 ], "type": "text", "content": "BEGIN ATOMIC statement; {statement;...} END }" } ] } ], "index": 5, "angle": 0, "type": "code_body" } ], "index": 5, "sub_type": "code", "guess_lang": "typescript" }, { "type": "code", "bbox": [ 86, 219, 369, 294 ], "blocks": [ { "bbox": [ 86, 219, 369, 294 ], "lines": [ { "bbox": [ 86, 219, 369, 294 ], "spans": [ { "bbox": [ 86, 219, 369, 294 ], "type": "text", "content": "> 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。" } ] } ], "index": 6, "angle": 0, "type": "code_body" } ], "index": 6, "sub_type": "code", "guess_lang": "txt" }, { "bbox": [ 101, 296, 484, 312 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 98, 290, 487, 316 ], "spans": [ { "bbox": [ 98, 290, 487, 316 ], "type": "text", "content": "事件：BEFORE|AFTER{INSERT|DELETE| UPDATE..}", "score": 0.943 } ] } ] }, { "bbox": [ 101, 316, 571, 421 ], "type": "list", "angle": 0, "index": 11, "blocks": [ { "bbox": [ 101, 316, 562, 332 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 100, 314, 562, 333 ], "spans": [ { "bbox": [ 100, 314, 562, 333 ], "type": "text", "content": "□当一个事件(Insert,Delete,或Update)发生之前Before或发生之后After触发", "score": 0.972 } ] } ] }, { "bbox": [ 101, 336, 570, 368 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 101, 336, 571, 352 ], "spans": [ { "bbox": [ 101, 336, 571, 352 ], "type": "text", "content": "□DELETE/INSERT/UPDATE操作发生，执行触发器操作需处理两组值：更新前", "score": 0.993 } ] }, { "bbox": [ 120, 351, 486, 369 ], "spans": [ { "bbox": [ 120, 351, 486, 369 ], "type": "text", "content": "的值和更新后的值，这两个值由corr_name_def的使用来区分", "score": 0.997 } ] } ] }, { "bbox": [ 101, 373, 571, 421 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 103, 374, 570, 388 ], "spans": [ { "bbox": [ 103, 374, 570, 388 ], "type": "text", "content": "□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", "score": 0.997 } ] }, { "bbox": [ 120, 389, 565, 405 ], "spans": [ { "bbox": [ 120, 389, 565, 405 ], "type": "text", "content": "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", "score": 0.998 } ] }, { "bbox": [ 119, 404, 170, 423 ], "spans": [ { "bbox": [ 119, 404, 170, 423 ], "type": "text", "content": "触发器。", "score": 0.999 } ] } ] } ], "sub_type": "text" }, { "type": "code", "bbox": [ 94, 431, 381, 531 ], "blocks": [ { "bbox": [ 94, 431, 381, 531 ], "lines": [ { "bbox": [ 94, 431, 381, 531 ], "spans": [ { "bbox": [ 94, 431, 381, 531 ], "type": "text", "content": "CREATE 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}" } ] } ], "index": 12, "angle": 0, "type": "code_body" } ], "index": 12, "sub_type": "code", "guess_lang": "sql" }, { "type": "image", "bbox": [ 402, 437, 571, 515 ], "blocks": [ { "bbox": [ 402, 437, 571, 515 ], "lines": [ { "bbox": [ 402, 437, 571, 515 ], "spans": [ { "bbox": [ 402, 437, 571, 515 ], "type": "image", "image_path": "97868f142be5baa0f0e5950e2a9471a66963130572466d4d12982117187ddefe.jpg" } ] } ], "index": 13, "angle": 0, "type": "image_body" } ], "index": 13 }, { "bbox": [ 86, 561, 229, 574 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 561, 229, 576 ], "spans": [ { "bbox": [ 89, 561, 229, 576 ], "type": "text", "content": "属性上的约束条件：NOT NULL", "score": 1.0 } ] } ] }, { "bbox": [ 87, 577, 126, 589 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 577, 127, 592 ], "spans": [ { "bbox": [ 88, 577, 127, 592 ], "type": "text", "content": "UNIQUE", "score": 1.0 } ] } ] }, { "bbox": [ 87, 593, 119, 603 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 594, 120, 608 ], "spans": [ { "bbox": [ 88, 594, 120, 608 ], "type": "text", "content": "CHECK", "score": 1.0 } ] } ] }, { "bbox": [ 87, 608, 306, 621 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 608, 307, 624 ], "spans": [ { "bbox": [ 88, 608, 307, 624 ], "type": "text", "content": "表上的约束条件 CASCADDE NO ACTION RESTRICT", "score": 1.0 } ] } ] }, { "bbox": [ 86, 640, 138, 652 ], "type": "title", "angle": 0, "index": 18, "lines": [ { "bbox": [ 87, 640, 139, 655 ], "spans": [ { "bbox": [ 87, 640, 139, 655 ], "type": "text", "content": "2.1 安全性", "score": 1.0 } ] } ] }, { "bbox": [ 86, 655, 227, 667 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 655, 227, 670 ], "spans": [ { "bbox": [ 88, 655, 227, 670 ], "type": "text", "content": "考核要求：达到“识记”层次", "score": 1.0 } ] } ] }, { "bbox": [ 87, 671, 185, 683 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 88, 669, 186, 686 ], "spans": [ { "bbox": [ 88, 669, 186, 686 ], "type": "text", "content": "知识点：安全性定义", "score": 1.0 } ] } ] }, { "bbox": [ 86, 702, 346, 714 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 702, 348, 717 ], "spans": [ { "bbox": [ 88, 702, 348, 717 ], "type": "text", "content": "数据库的完整性是指尽可能避免对数据库的无意的滥用；", "score": 1.0 } ] } ] }, { "bbox": [ 86, 718, 346, 730 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 89, 719, 347, 731 ], "spans": [ { "bbox": [ 89, 719, 347, 731 ], "type": "text", "content": "数据库的安全性是指尽可能避免对数据库的恶意的滥用。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 749, 430, 761 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 88, 749, 431, 763 ], "spans": [ { "bbox": [ 88, 749, 431, 763 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 24 }, { "para_blocks": [ { "bbox": [ 94, 79, 192, 153 ], "type": "list", "angle": 0, "index": 5, "blocks": [ { "bbox": [ 94, 79, 192, 91 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": 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324, 293 ], "type": "inline_equation", "content": ">", "score": 0.65 }, { "bbox": [ 324, 279, 374, 298 ], "type": "text", "content": "[CASCADE]", "score": 1.0 } ] } ] }, { "bbox": [ 86, 296, 426, 310 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 297, 426, 310 ], "spans": [ { "bbox": [ 88, 297, 426, 310 ], "type": "text", "content": "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", "score": 1.0 } ] } ] }, { "bbox": [ 86, 312, 503, 341 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 132, 314, 503, 325 ], "spans": [ { "bbox": [ 132, 314, 503, 325 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 328, 423, 341 ], "spans": [ { "bbox": [ 89, 328, 423, 341 ], "type": "text", "content": "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）", "score": 1.0 } ] } ] }, { "bbox": [ 86, 343, 503, 372 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 89, 345, 504, 356 ], "spans": [ { "bbox": [ 89, 345, 504, 356 ], 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158, 481 ], "spans": [ { "bbox": [ 88, 469, 158, 481 ], "type": "text", "content": "3.2 事务的性质", "score": 1.0 } ] } ] }, { "bbox": [ 86, 499, 172, 512 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 88, 499, 174, 514 ], "spans": [ { "bbox": [ 88, 499, 174, 514 ], "type": "text", "content": "事务的ACID性质：", "score": 1.0 } ] } ] }, { "bbox": [ 86, 515, 442, 529 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 87, 513, 445, 531 ], "spans": [ { "bbox": [ 87, 513, 445, 531 ], "type": "text", "content": "原子性(atomicity)、一致性(consistency)、隔离性(isolation)和持久性(durability)。", "score": 1.0 } ] } ] }, { "type": "table", "bbox": [ 94, 560, 508, 721 ], "blocks": [ { "bbox": [ 87, 546, 201, 559 ], "lines": [ { "bbox": [ 88, 547, 200, 560 ], "spans": [ { "bbox": [ 88, 547, 200, 560 ], "type": "text", "content": "3.3 故障类型和恢复方法", "score": 1.0 } ] } ], "index": 10, "angle": 0, "type": "table_caption" }, { "bbox": [ 94, 560, 508, 721 ], "lines": [ { "bbox": [ 94, 560, 508, 721 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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
", "image_path": "5871e608b3293f44e6bc1fa38c3818b22bf0f44364ad5c0253c4efb95cd1c791.jpg" } ] } ], "index": 11, "angle": 0, "type": "table_body" } ], "index": 11 } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 26 }, { "para_blocks": [ { "bbox": [ 88, 95, 232, 107 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 95, 232, 109 ], "spans": [ { "bbox": [ 88, 95, 232, 109 ], "type": "text", "content": "3.4 恢复的基本原则和实现方法", "score": 1.0 } ] } ] }, { "bbox": [ 86, 125, 367, 138 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 89, 125, 368, 139 ], "spans": [ { "bbox": [ 89, 125, 368, 139 ], "type": "text", "content": "恢复的基本原则很简单，就是“冗余”，即数据的重复存储。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 142, 146, 153 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 89, 142, 149, 155 ], "spans": [ { "bbox": [ 89, 142, 149, 155 ], "type": "text", "content": "实现方法有：", "score": 1.0 } ] } ] }, { "bbox": [ 87, 157, 273, 169 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 156, 274, 172 ], "spans": [ { "bbox": [ 88, 156, 274, 172 ], "type": "text", "content": "(1)定期对数据库进行复制或转储(dump)。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 173, 376, 185 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 173, 377, 185 ], "spans": [ { "bbox": [ 88, 173, 377, 185 ], "type": "text", "content": "Notice:几个概念：静态转储、动态转储、海量转储和增量转储。", "score": 1.0 } ] } ] }, { "bbox": [ 104, 188, 503, 263 ], "type": "list", "angle": 0, "index": 9, "blocks": [ { "bbox": [ 104, 188, 424, 200 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 123, 188, 426, 202 ], "spans": [ { "bbox": [ 123, 188, 426, 202 ], "type": "text", "content": "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；", "score": 1.0 } ] } ] }, { "bbox": [ 104, 203, 503, 232 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 123, 203, 504, 216 ], "spans": [ { "bbox": [ 123, 203, 504, 216 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 123, 216, 155, 235 ], "spans": [ { "bbox": [ 123, 216, 155, 235 ], "type": "text", "content": "执行；", "score": 1.0 } ] } ] }, { "bbox": [ 104, 235, 287, 247 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 123, 235, 289, 248 ], "spans": [ { "bbox": [ 123, 235, 289, 248 ], "type": "text", "content": "海量存储是指每次转储全部数据库；", "score": 1.0 } ] } ] }, { "bbox": [ 104, 250, 360, 263 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 123, 251, 361, 264 ], "spans": [ { "bbox": [ 123, 251, 361, 264 ], "type": "text", "content": "增量存储则指每次只转储上次转储后更新过的数据。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 87, 266, 190, 279 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 88, 265, 191, 280 ], "spans": [ { "bbox": [ 88, 265, 191, 280 ], "type": "text", "content": "(2)建立“日志”文件。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 281, 504, 325 ], "type": "text", "angle": 0, "index": 11, 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257
723
443
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S:ABC
345
723
", "image_path": "c1f2a8421f4e33b65536738618c420f7cea8e1858f3d3b426ea8f199c3818b5c.jpg" } ] } ], "index": 21, "angle": 0, "type": "table_body" } ], "index": 21 }, { "bbox": [ 87, 608, 116, 621 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 607, 119, 624 ], "spans": [ { "bbox": [ 88, 607, 119, 624 ], "type": "text", "content": "计算：", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 30 }, { "para_blocks": [ { "bbox": [ 94, 81, 428, 107 ], "type": "text", "angle": 0, "index": 0, "lines": [] }, { "bbox": [ 94, 123, 123, 139 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 92, 123, 126, 143 ], "spans": [ { "bbox": [ 92, 123, 126, 143 ], "type": "text", "content": "RUS", "score": 0.847 } ] } ] }, { "type": "table", "bbox": [ 135, 121, 217, 214 ], "blocks": [ { "bbox": [ 135, 121, 217, 214 ], "lines": [ { "bbox": [ 135, 121, 217, 214 ], "spans": [ { "bbox": [ 135, 121, 217, 214 ], "type": "table", "html": "
ABC
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257
723
443
345
", "image_path": "00455de20c2cf426148ddc49a70c009b187c99b18483cd9f83f0506c4b5854e3.jpg" } ] } ], "index": 2, "angle": 0, "type": "table_body" } ], "index": 2 }, { "type": "table", "bbox": [ 248, 119, 352, 190 ], "blocks": [ { "bbox": [ 248, 119, 352, 190 ], "lines": [ { "bbox": [ 248, 119, 352, 190 ], "spans": [ { "bbox": [ 248, 119, 352, 190 ], "type": "table", "html": "
R-SABC
367
257
443
", "image_path": "d279de62defc274697015c4257a93a4329c3abdfde3c9ff6b0a60e3b6b408f83.jpg" } ] } ], "index": 3, "angle": 0, "type": "table_body" } ], "index": 3 }, { "bbox": [ 375, 131, 402, 147 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 373, 129, 406, 150 ], "spans": [ { "bbox": [ 373, 129, 406, 150 ], "type": "text", "content": "Rns", "score": 0.597 } ] } ] }, { "type": "table", "bbox": [ 407, 125, 488, 178 ], "blocks": [ { "bbox": [ 407, 125, 488, 178 ], "lines": [ { "bbox": [ 407, 125, 488, 178 ], "spans": [ { "bbox": [ 407, 125, 488, 178 ], "type": "table", "html": "
ABC
723
", "image_path": "93ed466fae3892b534eddcaca7e87f2cf55bb9e84dfa9486f0596726040b9020.jpg" } ] } ], "index": 5, "angle": 0, "type": "table_body" } ], "index": 5 }, { "type": "table", "bbox": [ 93, 238, 282, 371 ], "blocks": [ { "bbox": [ 93, 238, 282, 371 ], "lines": [ { "bbox": [ 93, 238, 282, 371 ], "spans": [ { "bbox": [ 93, 238, 282, 371 ], "type": "table", "html": "
R×SR.AR.BR.CS.AS.BS.C
367345
367723
257345
257723
723345
723723
443345
443723
", "image_path": "f7a972290b997ac1e67f97dde32f8d7c5283063ac9bf65af4db97d53c8a781bd.jpg" } ] } ], "index": 6, "angle": 0, "type": "table_body" } ], "index": 6 }, { "type": "table", "bbox": [ 305, 238, 491, 380 ], "blocks": [ { "bbox": [ 305, 238, 491, 380 ], "lines": [ { "bbox": [ 305, 238, 491, 380 ], "spans": [ { "bbox": [ 305, 238, 491, 380 ], "type": "table", "html": "
π3,2(S)σB<',5'(R)
CBABC
54723
32443
R×S2<2R.AR.BR.CS.AS.BS.C
723345
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ABC
723
", "image_path": "503e73dd9a26c985fd2541af47e6ef25ee480fb8c5483f8a0e76437ee8c45f0f.jpg" } ] } ], "index": 9, "angle": 0, "type": "table_body" } ], "index": 9 }, { "bbox": [ 86, 468, 504, 497 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 89, 469, 504, 481 ], "spans": [ { "bbox": [ 89, 469, 504, 481 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 485, 379, 497 ], "spans": [ { "bbox": [ 89, 485, 379, 497 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 93, 500, 289, 512 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 95, 500, 289, 513 ], "spans": [ { "bbox": [ 95, 500, 289, 513 ], "type": "text", "content": "（1）在列关系表达式时，通常有以下形式：", "score": 1.0 } ] } ] }, { "bbox": [ 86, 516, 229, 528 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 88, 514, 230, 530 ], "spans": [ { "bbox": [ 88, 516, 145, 528 ], "type": "inline_equation", "content": "\\pi . . . ( \\sigma . . ( \\mathsf { R } { \\times } \\mathsf { S } ) )", "score": 0.82 }, { "bbox": [ 145, 514, 230, 530 ], "type": "text", "content": "或者 π...(σ...(R S))", "score": 1.0 } ] } ] }, { "bbox": [ 86, 530, 504, 559 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 89, 531, 505, 544 ], "spans": [ { "bbox": [ 89, 531, 505, 544 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 547, 317, 558 ], "spans": [ { "bbox": [ 89, 547, 317, 558 ], "type": "text", "content": "大表格执行水平分割(选择)和垂直分割(投影)操作。", "score": 1.0 } ] } ] }, { "bbox": [ 92, 562, 404, 575 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 95, 561, 405, 576 ], "spans": [ { "bbox": [ 95, 561, 405, 576 ], "type": "text", "content": "（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。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 577, 236, 590 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 89, 576, 238, 594 ], "spans": [ { "bbox": [ 89, 576, 238, 594 ], "type": "text", "content": "学生关系 S(SNO,SNAME,AGE,SEX)", "score": 1.0 } ] } ] }, { "bbox": [ 110, 593, 247, 606 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 112, 592, 248, 609 ], "spans": [ { "bbox": [ 112, 592, 248, 609 ], "type": "text", "content": "学习关系 SC(SNO,CNO,GRADE)", "score": 1.0 } ] } ] }, { "bbox": [ 111, 608, 265, 622 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 112, 608, 266, 624 ], "spans": [ { "bbox": [ 112, 608, 266, 624 ], "type": "text", "content": "课程关系 C(CNO,CNAME,TEACHER)", "score": 1.0 } ] } ] }, { "bbox": [ 99, 624, 295, 637 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 102, 624, 296, 638 ], "spans": [ { "bbox": [ 102, 624, 296, 638 ], "type": "text", "content": "下面用关系代数表达式表达每个查询语句。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 640, 291, 653 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 88, 640, 292, 655 ], "spans": [ { "bbox": [ 88, 640, 292, 655 ], "type": "text", "content": "(1) 检索学习课程号为 C2 的学生学号与成绩。", "score": 1.0 } ] } ] }, { "bbox": [ 96, 656, 195, 669 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 656, 195, 669 ], "spans": [ { "bbox": [ 96, 656, 195, 669 ], "type": "interline_equation", "content": "\\pi_ {\\mathrm {S N O}, \\text {G R A D E}} (\\sigma_ {\\mathrm {C N O} = ^ {\\prime} \\mathrm {C 2} ^ {\\prime}} (\\mathrm {S C}))", "image_path": "e618f04cf3f6c98899bb55797c516781aae58868acf9490aba3b926b72097504.jpg" } ] } ], "index": 20 }, { "bbox": [ 87, 671, 286, 684 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 88, 671, 286, 685 ], "spans": [ { "bbox": [ 88, 671, 286, 685 ], "type": "text", "content": "(2) 检索学习课程号为C2的学生学号与姓名", "score": 1.0 } ] } ] }, { "bbox": [ 93, 687, 209, 700 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 93, 687, 209, 700 ], "spans": [ { "bbox": [ 93, 687, 209, 700 ], "type": "interline_equation", "content": "\\pi_ {S N O, S N A M E} \\left(\\sigma_ {C N O = ^ {\\prime} C 2 ^ {\\prime}} (S \\times S C)\\right)", "image_path": "2bcb83724afc6de0e7ba16f184b498c2f9fab9009a78ddce43f26008427f6e20.jpg" } ] } ], "index": 22 }, { "bbox": [ 86, 702, 504, 730 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 99, 703, 505, 715 ], "spans": [ { "bbox": [ 99, 703, 505, 715 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 718, 284, 730 ], "spans": [ { "bbox": [ 88, 718, 284, 730 ], "type": "text", "content": "的有关的信息，然后再执行选择投影操作。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 734, 199, 746 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 89, 734, 199, 747 ], "spans": [ { "bbox": [ 89, 734, 199, 747 ], "type": "text", "content": "此查询亦可等价地写成：", "score": 1.0 } ] } ] }, { "bbox": [ 96, 749, 264, 762 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 749, 264, 762 ], "spans": [ { "bbox": [ 96, 749, 264, 762 ], "type": "interline_equation", "content": "\\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})))", "image_path": "a19c07c41b4261d18a9024df4fa26f330f01a40c4051e176fc76ec7900cfd6fd.jpg" } ] } ], "index": 25 } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 31 }, { "para_blocks": [ { "bbox": [ 86, 79, 505, 107 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 98, 79, 505, 91 ], "spans": [ { "bbox": [ 98, 79, 505, 91 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 95, 283, 108 ], "spans": [ { "bbox": [ 89, 95, 283, 108 ], "type": "text", "content": "表达式优化，执行起来要省时间，省空间。", "score": 1.0 } ] } ] }, { "bbox": [ 93, 110, 324, 122 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 95, 110, 324, 124 ], "spans": [ { "bbox": [ 95, 110, 324, 124 ], "type": "text", "content": "（3）检索选修课程名为 MATHS 的学生学号与姓名。", "score": 1.0 } ] } ] }, { "bbox": [ 96, 126, 246, 139 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 126, 246, 139 ], "spans": [ { "bbox": [ 96, 126, 246, 139 ], "type": "interline_equation", "content": "\\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)", "image_path": "70df10f1abb4a5ce03f24333a78fa5d20f48e0997ff40fa43e093bf3840a4a28.jpg" } ] } ], "index": 2 }, { "bbox": [ 94, 141, 298, 153 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 95, 141, 298, 155 ], "spans": [ { "bbox": [ 95, 141, 298, 155 ], "type": "text", "content": "（4）检索选修课程号为C2或C4的学生学号。", "score": 1.0 } ] } ] }, { "bbox": [ 96, 157, 199, 169 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 157, 199, 169 ], "spans": [ { "bbox": [ 96, 157, 199, 169 ], "type": "interline_equation", "content": "\\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)", "image_path": "f1297846dd314999c9d93d19ce82777c5f6f16302e7b18bc2641079beb2a3968.jpg" } ] } ], "index": 4 }, { "bbox": [ 94, 172, 321, 185 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 95, 172, 322, 187 ], "spans": [ { "bbox": [ 95, 172, 322, 187 ], "type": "text", "content": "（5） 检索至少选修课程号为 C2 或 C4 的学生学号。", "score": 1.0 } ] } ] }, { "bbox": [ 96, 188, 218, 201 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 188, 218, 201 ], "spans": [ { "bbox": [ 96, 188, 218, 201 ], "type": "interline_equation", "content": "\\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)", "image_path": "d3f16428529e2d93346b06ad51a870d72df4e0a39d4deff2673b479a50264030.jpg" } ] } ], "index": 6 }, { "bbox": [ 86, 203, 504, 232 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 104, 204, 505, 216 ], "spans": [ { "bbox": [ 104, 204, 136, 216 ], "type": "text", "content": "这里（", "score": 1.0 }, { "bbox": [ 136, 204, 166, 216 ], "type": "inline_equation", "content": "5 C { \\times } 5 C", "score": 0.8 }, { "bbox": [ 166, 204, 505, 216 ], "type": "text", "content": "）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", "score": 1.0 } ] }, { "bbox": [ 89, 220, 402, 232 ], "spans": [ { "bbox": [ 89, 220, 402, 232 ], "type": "text", "content": "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：", "score": 1.0 } ] } ] }, { "bbox": [ 86, 235, 243, 248 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 86, 235, 243, 248 ], "spans": [ { "bbox": [ 86, 235, 243, 248 ], "type": "interline_equation", "content": "\\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)", "image_path": "60606af738a48d58528af30f4f48351bbb7012f5a0ed1cf812cfe1dacc0163fd.jpg" } ] } ], "index": 8 }, { "bbox": [ 93, 250, 274, 263 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 95, 250, 275, 264 ], "spans": [ { "bbox": [ 95, 250, 275, 264 ], "type": "text", "content": "（6） 检索不学C2课的学生姓名与年龄。", "score": 1.0 } ] } ] }, { "bbox": [ 96, 266, 303, 280 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 266, 303, 280 ], "spans": [ { "bbox": [ 96, 266, 303, 280 ], "type": "interline_equation", "content": "\\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)", "image_path": "4f9bb565c05889ea05ff6b5c705f8c0fa4322c18cc16d071ecc9f9e124ec53c1.jpg" } ] } ], "index": 10 }, { "bbox": [ 86, 281, 505, 310 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 98, 281, 506, 295 ], "spans": [ { "bbox": [ 98, 281, 506, 295 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 297, 195, 312 ], "spans": [ { "bbox": [ 88, 297, 195, 312 ], "type": "text", "content": "课的学生姓名与年龄\"。", "score": 1.0 } ] } ] }, { "bbox": [ 93, 312, 257, 326 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 95, 312, 258, 327 ], "spans": [ { "bbox": [ 95, 312, 258, 327 ], "type": "text", "content": "（7）检索学习全部课程的学生姓名。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 328, 273, 341 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 89, 329, 273, 342 ], "spans": [ { "bbox": [ 89, 329, 273, 342 ], "type": "text", "content": "编写这个查询语句的关系代数过程如下：", "score": 1.0 } ] } ] }, { "bbox": [ 87, 343, 307, 388 ], "type": "list", "angle": 0, "index": 17, "blocks": [ { "bbox": [ 87, 343, 262, 357 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 343, 264, 359 ], "spans": [ { "bbox": [ 88, 343, 188, 359 ], "type": "text", "content": "(a) 学生选课情况可用", "score": 1.0 }, { "bbox": [ 188, 344, 236, 357 ], "type": "inline_equation", "content": "\\pi _ { \\mathsf { S N O , C N O } } ( \\mathsf { S C } )", "score": 0.85 }, { "bbox": [ 236, 343, 264, 359 ], "type": "text", "content": "表示；", "score": 1.0 } ] } ] }, { "bbox": [ 88, 359, 224, 373 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 359, 226, 375 ], "spans": [ { "bbox": [ 88, 359, 167, 375 ], "type": "text", "content": "(b) 全部课程可用", "score": 1.0 }, { "bbox": [ 167, 360, 198, 373 ], "type": "inline_equation", "content": "\\pi _ { \\mathsf { C N O } } ( \\mathsf { C } )", "score": 0.9 }, { "bbox": [ 198, 359, 226, 375 ], "type": "text", "content": "表示；", "score": 1.0 } ] } ] }, { "bbox": [ 87, 375, 307, 388 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 88, 375, 307, 389 ], "spans": [ { "bbox": [ 88, 375, 307, 389 ], "type": "text", "content": "(c) 学了全部课程的学生学号可用除法操作表示。", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 86, 391, 505, 434 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 108, 391, 505, 403 ], "spans": [ { "bbox": [ 108, 391, 505, 403 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 407, 505, 420 ], "spans": [ { "bbox": [ 88, 407, 505, 420 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 423, 242, 434 ], "spans": [ { "bbox": [ 89, 423, 242, 434 ], "type": "text", "content": "课程（这是\"除法\"操作的含义）：", "score": 1.0 } ] } ] }, { "bbox": [ 96, 438, 181, 450 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 438, 181, 450 ], "spans": [ { "bbox": [ 96, 438, 181, 450 ], "type": "interline_equation", "content": "\\pi_ {\\mathrm {S N O}, \\mathrm {C N O}} (\\mathrm {S C}) \\div \\pi_ {\\mathrm {C N O}} (\\mathrm {C})", "image_path": "af972176132ec4d6dea1074ae82b78835071c293b7b352f55863126d49645f0f.jpg" } ] } ], "index": 19 }, { "bbox": [ 87, 453, 406, 465 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 88, 452, 408, 468 ], "spans": [ { "bbox": [ 88, 452, 408, 468 ], "type": "text", "content": "(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：", "score": 1.0 } ] } ] }, { "bbox": [ 96, 469, 236, 481 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 469, 236, 481 ], "spans": [ { "bbox": [ 96, 469, 236, 481 ], "type": "interline_equation", "content": "\\pi_ {S N A M E} (S \\boxtimes (\\pi_ {S N O, C N O} (S C) \\div \\pi_ {C N O} (C)))", "image_path": "f4998326c9d5a4c13009794f1edc4c2a13ea0e596c263773ad05865312c75bfc.jpg" } ] } ], "index": 21 }, { "bbox": [ 86, 483, 252, 497 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 88, 484, 251, 498 ], "spans": [ { "bbox": [ 88, 484, 251, 498 ], "type": "text", "content": "这就是最后得到的关系代数表达式。", "score": 1.0 } ] } ] }, { "bbox": [ 93, 500, 315, 512 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 95, 499, 317, 513 ], "spans": [ { "bbox": [ 95, 499, 317, 513 ], "type": "text", "content": "（8） 检索所学课程包含S3所学课程的学生学号。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 515, 423, 528 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 88, 515, 424, 529 ], "spans": [ { "bbox": [ 88, 515, 424, 529 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 100, 530, 285, 544 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 102, 529, 287, 546 ], "spans": [ { "bbox": [ 102, 529, 287, 546 ], "type": "text", "content": "学生选课情况可用操作 πSNO,CNO(SC)表示；", "score": 1.0 } ] } ] }, { "bbox": [ 100, 546, 406, 560 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 102, 547, 408, 560 ], "spans": [ { "bbox": [ 102, 547, 408, 560 ], "type": "text", "content": "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：", "score": 1.0 } ] } ] }, { "bbox": [ 96, 563, 229, 576 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 96, 563, 229, 576 ], "spans": [ { "bbox": [ 96, 563, 229, 576 ], "type": "interline_equation", "content": "\\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)", "image_path": "4b3a5a8fd610eeaa8e87dd78816e8169811b78694acce0c2798ed129a4d70369.jpg" } ] } ], "index": 27 } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 32 }, { "para_blocks": [ { "bbox": [ 94, 79, 376, 92 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 96, 79, 376, 91 ], "spans": [ { "bbox": [ 96, 79, 376, 91 ], "type": "text", "content": "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。", "score": 0.999 } ] } ] }, { "bbox": [ 94, 95, 498, 123 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 96, 95, 498, 108 ], "spans": [ { "bbox": [ 96, 95, 498, 108 ], "type": "text", "content": "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", "score": 0.994 } ] }, { "bbox": [ 96, 111, 236, 123 ], "spans": [ { "bbox": [ 96, 111, 236, 123 ], "type": "text", "content": "接运算却往往花费教多的时间。", "score": 0.999 } ] } ] }, { "bbox": [ 94, 126, 498, 156 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 96, 126, 499, 140 ], "spans": [ { "bbox": [ 96, 126, 499, 140 ], "type": "text", "content": "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", "score": 0.996 } ] }, { "bbox": [ 97, 143, 365, 155 ], "spans": [ { "bbox": [ 97, 143, 365, 155 ], "type": "text", "content": "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。", "score": 0.997 } ] } ] }, { "bbox": [ 94, 169, 290, 185 ], "type": "title", "angle": 0, "index": 3, "lines": [ { "bbox": [ 95, 169, 290, 185 ], "spans": [ { "bbox": [ 95, 169, 290, 185 ], "type": "text", "content": "3.2关系代数表达式的等价变换规则", "score": 1.0 } ] } ] }, { "bbox": [ 94, 186, 229, 200 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 96, 186, 229, 200 ], "spans": [ { "bbox": [ 96, 186, 229, 200 ], "type": "text", "content": "考核要求：达到”识记”层次", "score": 0.959 } ] } ] }, { "bbox": [ 95, 202, 198, 216 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 96, 203, 198, 216 ], "spans": [ { "bbox": [ 96, 203, 198, 216 ], "type": "text", "content": "知识点：等价变换规则", "score": 0.999 } ] } ] }, { "bbox": [ 94, 234, 493, 264 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 112, 235, 492, 247 ], "spans": [ { "bbox": [ 112, 235, 492, 247 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 95, 250, 186, 264 ], "spans": [ { "bbox": [ 95, 250, 186, 264 ], "type": "text", "content": "结果是完全一样的。", "score": 0.998 } ] } ] }, { "bbox": [ 110, 266, 330, 280 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 111, 265, 332, 280 ], "spans": [ { "bbox": [ 111, 265, 332, 280 ], "type": "text", "content": "等价变换规则有很多，不要死记，从语义上理解。", "score": 1.0 } ] } ] }, { "bbox": [ 94, 282, 498, 312 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 96, 283, 498, 296 ], "spans": [ { "bbox": [ 96, 283, 498, 296 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 95, 298, 145, 312 ], "spans": [ { "bbox": [ 95, 298, 145, 312 ], "type": "text", "content": "是否等价。", "score": 0.992 } ] } ] }, { "bbox": [ 94, 328, 183, 343 ], "type": "title", "angle": 0, "index": 9, "lines": [ { "bbox": [ 95, 328, 183, 344 ], "spans": [ { "bbox": [ 95, 328, 183, 344 ], "type": "text", "content": "3.3优化的策略", "score": 0.999 } ] } ] }, { "bbox": [ 94, 346, 229, 359 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 95, 346, 229, 360 ], "spans": [ { "bbox": [ 95, 346, 229, 360 ], "type": "text", "content": "考核要求：达到”领会”层次", "score": 0.984 } ] } ] }, { "bbox": [ 95, 362, 248, 375 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 96, 363, 248, 375 ], "spans": [ { "bbox": [ 96, 363, 248, 375 ], "type": "text", "content": "知识点：优化的策略及其简单应用", "score": 0.998 } ] } ] }, { "bbox": [ 94, 394, 224, 407 ], "type": "text", "angle": 0, "index": 12, "lines": [ { "bbox": [ 96, 394, 226, 407 ], "spans": [ { "bbox": [ 96, 394, 226, 407 ], "type": "text", "content": "优化的策略主要有以下几点：", "score": 1.0 } ] } ] }, { "bbox": [ 94, 410, 329, 502 ], "type": "list", "angle": 0, "index": 19, "blocks": [ { "bbox": [ 94, 410, 320, 423 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 95, 410, 321, 423 ], "spans": [ { "bbox": [ 95, 410, 321, 423 ], "type": "text", "content": "(1)在关系代数表达式中尽可能早地执行选择操作；", "score": 0.979 } ] } ] }, { "bbox": [ 94, 426, 329, 439 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 95, 426, 332, 439 ], "spans": [ { "bbox": [ 95, 426, 332, 439 ], "type": "text", "content": "(2)把笛卡尔积和随后的选择操作合并成F连接运算；", "score": 0.985 } ] } ] }, { "bbox": [ 95, 442, 270, 454 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 95, 442, 271, 454 ], "spans": [ { "bbox": [ 95, 442, 271, 454 ], "type": "text", "content": "(3)同时计算一连串的选择和投影操作；", "score": 0.98 } ] } ] }, { "bbox": [ 95, 458, 230, 470 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 96, 459, 231, 470 ], "spans": [ { "bbox": [ 96, 459, 231, 470 ], "type": "text", "content": "（4)保留同一子表达式的结果；", "score": 0.965 } ] } ] }, { "bbox": [ 95, 474, 244, 486 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 95, 474, 246, 488 ], "spans": [ { "bbox": [ 95, 474, 246, 488 ], "type": "text", "content": "(5)适当对关系文件进行预处理；", "score": 0.984 } ] } ] }, { "bbox": [ 95, 490, 299, 502 ], "type": "text", "angle": 0, "index": 18, "lines": [ { "bbox": [ 95, 490, 301, 503 ], "spans": [ { "bbox": [ 95, 490, 301, 503 ], "type": "text", "content": "(6)计算表达式之前先估计一下怎么计算合算。", "score": 0.99 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 94, 521, 415, 534 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 96, 521, 416, 535 ], "spans": [ { "bbox": [ 96, 521, 416, 535 ], "type": "text", "content": "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。", "score": 0.999 } ] } ] }, { "bbox": [ 94, 552, 266, 566 ], "type": "title", "angle": 0, "index": 21, "lines": [ { "bbox": [ 95, 553, 266, 568 ], "spans": [ { "bbox": [ 95, 553, 266, 568 ], "type": "text", "content": "3.4关系代数表达式的优化算法", "score": 1.0 } ] } ] }, { "bbox": [ 94, 569, 248, 582 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 96, 569, 248, 583 ], "spans": [ { "bbox": [ 96, 569, 248, 583 ], "type": "text", "content": "考核要求：达到”简单应用”层次", "score": 0.987 } ] } ] }, { "bbox": [ 95, 586, 168, 598 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 95, 586, 168, 598 ], "spans": [ { "bbox": [ 95, 586, 168, 598 ], "type": "text", "content": "知识点：语法树", "score": 0.998 } ] } ] }, { "bbox": [ 94, 617, 244, 630 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 96, 618, 246, 631 ], "spans": [ { "bbox": [ 96, 618, 246, 631 ], "type": "text", "content": "学会画语法树，并掌握优化算法。", "score": 0.999 } ] } ] }, { "bbox": [ 95, 649, 117, 661 ], "type": "title", "angle": 0, "index": 25, "lines": [ { "bbox": [ 95, 647, 120, 666 ], "spans": [ { "bbox": [ 95, 647, 120, 666 ], "type": "text", "content": "举例", "score": 1.0 } ] } ] }, { "bbox": [ 94, 667, 500, 681 ], "type": "text", "angle": 0, "index": 26, "lines": [ { "bbox": [ 96, 667, 502, 681 ], "spans": [ { "bbox": [ 96, 667, 502, 681 ], "type": "text", "content": "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。", "score": 0.966 } ] } ] }, { "bbox": [ 94, 686, 430, 752 ], "type": "list", "angle": 0, "index": 31, "blocks": [ { "bbox": [ 94, 686, 259, 698 ], "type": "text", "angle": 0, "index": 27, "lines": [ { "bbox": [ 95, 686, 261, 698 ], "spans": [ { "bbox": [ 95, 686, 261, 698 ], "type": "text", "content": "（1)试写出该查询的关系代数表达式；", "score": 0.984 } ] } ] }, { "bbox": [ 94, 703, 270, 716 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 95, 703, 271, 717 ], "spans": [ { "bbox": [ 95, 703, 271, 717 ], "type": "text", "content": "(2)试写出查询优化的关系代数表达式；", "score": 0.972 } ] } ] }, { "bbox": [ 94, 721, 309, 734 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 95, 721, 311, 735 ], "spans": [ { "bbox": [ 95, 721, 311, 735 ], "type": "text", "content": "(3)画出该查询初始的关系代数表达式的语法树；", "score": 0.973 } ] } ] }, { "bbox": [ 94, 739, 430, 752 ], "type": "text", "angle": 0, "index": 30, "lines": [ { "bbox": [ 95, 739, 431, 754 ], "spans": [ { "bbox": [ 95, 739, 431, 754 ], "type": "text", "content": "(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。", "score": 0.992 } ] } ] } ], "sub_type": "text" } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 33 }, { "para_blocks": [ { "bbox": [ 87, 111, 338, 139 ], "type": "list", "angle": 0, "index": 2, "blocks": [ { "bbox": [ 87, 111, 229, 123 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 111, 230, 125 ], "spans": [ { "bbox": [ 88, 111, 230, 125 ], "type": "text", "content": "(1)πCNAME,TEACHER(σSEX='女'(S SC C))", "score": 1.0 } ] } ] }, { "bbox": [ 87, 126, 338, 139 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 88, 125, 337, 142 ], "spans": [ { "bbox": [ 88, 125, 139, 142 ], "type": "text", "content": "(2)优化为：", "score": 1.0 }, { "bbox": [ 140, 126, 337, 139 ], "type": "inline_equation", "content": "\\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", "score": 0.54 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 87, 141, 496, 154 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 89, 142, 498, 154 ], "spans": [ { "bbox": [ 89, 142, 498, 154 ], "type": "text", "content": "(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。", "score": 1.0 } ] } ] }, { "type": "image", "bbox": [ 128, 161, 274, 366 ], "blocks": [ { "bbox": [ 128, 161, 274, 366 ], "lines": [ { "bbox": [ 128, 161, 274, 366 ], "spans": [ { "bbox": [ 128, 161, 274, 366 ], "type": "image", "image_path": "c5cf98588f1c817af21465451f17d7e9f054f7bca7a17b1c8e3429dea7fae0c5.jpg" } ] } ], "index": 4, "angle": 0, "type": "image_body" } ], "index": 4 }, { "type": "image", "bbox": [ 305, 158, 451, 384 ], "blocks": [ { "bbox": [ 305, 158, 451, 384 ], "lines": [ { "bbox": [ 305, 158, 451, 384 ], "spans": [ { "bbox": [ 305, 158, 451, 384 ], "type": "image", "image_path": "6131cc150d270daaf1dc47600b95b66abf7ade9afaefa725c74c406a4e9517c9.jpg" } ] } ], "index": 5, "angle": 0, "type": "image_body" } ], "index": 5 }, { "bbox": [ 86, 445, 420, 459 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 89, 446, 420, 460 ], "spans": [ { "bbox": [ 89, 446, 420, 460 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 461, 503, 506 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 88, 461, 505, 476 ], "spans": [ { "bbox": [ 88, 461, 505, 476 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 478, 504, 491 ], "spans": [ { "bbox": [ 89, 478, 504, 491 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 493, 168, 506 ], "spans": [ { "bbox": [ 89, 493, 168, 506 ], "type": "text", "content": "元组集合的描述。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 508, 503, 537 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 89, 509, 504, 522 ], "spans": [ { "bbox": [ 89, 509, 504, 522 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 524, 427, 538 ], "spans": [ { "bbox": [ 88, 524, 427, 538 ], "type": "text", "content": "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)。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 539, 472, 568 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 88, 539, 473, 553 ], "spans": [ { "bbox": [ 88, 539, 473, 553 ], "type": "text", "content": "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。", "score": 1.0 } ] }, { "bbox": [ 89, 556, 190, 568 ], "spans": [ { "bbox": [ 89, 556, 190, 568 ], "type": "text", "content": "核心内容是数据依赖。", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 34 }, { "para_blocks": [ { "bbox": [ 94, 84, 190, 100 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 92, 82, 192, 103 ], "spans": [ { "bbox": [ 92, 82, 192, 103 ], "type": "text", "content": "2函数依赖(FD", "score": 0.987 } ] } ] }, { "bbox": [ 101, 122, 212, 137 ], "type": "title", "angle": 0, "index": 1, "lines": [ { "bbox": [ 102, 122, 213, 137 ], "spans": [ { "bbox": [ 102, 122, 213, 137 ], "type": "text", "content": "2.1 函数依赖的定义", "score": 0.955 } ] } ] }, { "bbox": [ 101, 139, 235, 153 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 103, 140, 236, 153 ], "spans": [ { "bbox": [ 103, 140, 236, 153 ], "type": "text", "content": "考核要求：达到”领会”层次", "score": 0.996 } ] } ] }, { "bbox": [ 101, 156, 214, 169 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 103, 157, 214, 169 ], "spans": [ { "bbox": [ 103, 157, 214, 169 ], "type": "text", "content": "知识点：函数依赖的定义", "score": 0.997 } ] } ] }, { "bbox": [ 100, 187, 506, 232 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 122, 186, 505, 201 ], "spans": [ { "bbox": [ 122, 186, 505, 201 ], "type": "text", "content": "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", "score": 0.94 } ] }, { "bbox": [ 103, 204, 508, 216 ], "spans": [ { "bbox": [ 103, 204, 508, 216 ], "type": "text", "content": "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,", "score": 0.938 } ] }, { "bbox": [ 102, 219, 390, 232 ], "spans": [ { "bbox": [ 102, 219, 390, 232 ], "type": "text", "content": "或Y函数依赖于×，记为X→Y。X→Y为模式R的一个函数依赖。", "score": 0.974 } ] } ] }, { "bbox": [ 100, 251, 504, 296 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 123, 251, 502, 265 ], "spans": [ { "bbox": [ 123, 251, 502, 265 ], "type": "text", "content": "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", "score": 0.969 } ] }, { "bbox": [ 102, 267, 505, 280 ], "spans": [ { "bbox": [ 102, 267, 505, 280 ], "type": "text", "content": "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", "score": 0.996 } ] }, { "bbox": [ 103, 285, 250, 296 ], "spans": [ { "bbox": [ 103, 285, 250, 296 ], "type": "text", "content": "相等，这就是说Y函数依赖于X。", "score": 0.963 } ] } ] }, { "type": "table", "bbox": [ 89, 329, 335, 558 ], "blocks": [ { "bbox": [ 107, 315, 199, 327 ], "lines": [ { "bbox": [ 108, 315, 200, 329 ], "spans": [ { "bbox": [ 108, 315, 200, 329 ], "type": "text", "content": "比如，有如下二维表", "score": 0.998 } ] } ], "index": 6, "angle": 0, "type": "table_caption" }, { "bbox": [ 89, 329, 335, 558 ], "lines": [ { "bbox": [ 89, 329, 335, 558 ], "spans": [ { "bbox": [ 89, 329, 335, 558 ], "type": "table", "html": "
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
.....................
", "image_path": "6b67f4dc8d5af01b51a072f037f19df3f1b01c63795217e36a9bf97672f2e1bd.jpg" } ] } ], "index": 7, "angle": 0, "type": "table_body" } ], "index": 7 }, { "bbox": [ 93, 560, 514, 587 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 95, 559, 516, 572 ], "spans": [ { "bbox": [ 95, 559, 516, 572 ], "type": "text", "content": "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”。", "score": 0.969 } ] }, { "bbox": [ 95, 575, 196, 588 ], "spans": [ { "bbox": [ 95, 575, 196, 588 ], "type": "text", "content": "但是反过来则不成立。", "score": 0.998 } ] } ] }, { "bbox": [ 94, 592, 127, 602 ], "type": "title", "angle": 0, "index": 9, "lines": [] }, { "bbox": [ 93, 606, 513, 650 ], "type": "list", "angle": 0, "index": 12, "blocks": [ { "bbox": [ 93, 606, 513, 634 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 95, 606, 515, 619 ], "spans": [ { "bbox": [ 95, 606, 515, 619 ], "type": "text", "content": "(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，", "score": 0.998 } ] }, { "bbox": [ 95, 622, 254, 634 ], "spans": [ { "bbox": [ 95, 622, 254, 634 ], "type": "text", "content": "则函数依赖对于这个关系就不成立。", "score": 0.997 } ] } ] }, { "bbox": [ 94, 637, 380, 650 ], "type": "text", "angle": 0, "index": 11, "lines": [ { "bbox": [ 95, 637, 381, 650 ], "spans": [ { "bbox": [ 95, 637, 381, 650 ], "type": "text", "content": "(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.", "score": 0.997 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 86, 687, 220, 699 ], "type": "text", "angle": 0, "index": 13, "lines": [ { "bbox": [ 89, 687, 220, 699 ], "spans": [ { "bbox": [ 89, 687, 220, 699 ], "type": "text", "content": "码是唯一标识实体的属性集。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 702, 273, 714 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 88, 703, 274, 715 ], "spans": [ { "bbox": [ 88, 703, 274, 715 ], "type": "text", "content": "码和函数依赖的关系满足以下两个条件：", "score": 1.0 } ] } ] }, { "bbox": [ 86, 717, 447, 745 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 100, 717, 448, 731 ], "spans": [ { "bbox": [ 100, 717, 448, 731 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 734, 179, 746 ], "spans": [ { "bbox": [ 88, 734, 179, 746 ], "type": "text", "content": "(1)X→A1A2...An∈F+", "score": 1.0 } ] } ] }, { "bbox": [ 92, 749, 224, 762 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 92, 748, 225, 763 ], "spans": [ { "bbox": [ 92, 748, 225, 763 ], "type": "text", "content": "(X能够决定唯一的一个元组)", "score": 1.0 } ] } ] } ], "discarded_blocks": [], "page_size": [ 595, 841 ], "page_idx": 35 }, { "para_blocks": [ { "bbox": [ 86, 79, 307, 92 ], "type": "text", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 78, 307, 94 ], "spans": [ { "bbox": [ 88, 78, 307, 94 ], "type": "text", "content": "(2)不存在 X 的真子集 Y，使得 Y→A1A2...An 成立", "score": 1.0 } ] } ] }, { "bbox": [ 91, 95, 273, 107 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 93, 94, 273, 109 ], "spans": [ { "bbox": [ 93, 94, 273, 109 ], "type": "text", "content": "(X 能满足（1）但又没有多余的属性集）", "score": 1.0 } ] } ] }, { "bbox": [ 86, 110, 208, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 88, 110, 209, 124 ], "spans": [ { "bbox": [ 88, 110, 209, 124 ], "type": "text", "content": "则 X 就是 R 的一个候选码。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 125, 504, 154 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 89, 125, 505, 138 ], "spans": [ { "bbox": [ 89, 125, 505, 138 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 89, 142, 469, 153 ], "spans": [ { "bbox": [ 89, 142, 469, 153 ], "type": "text", "content": "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）。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 157, 460, 169 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 157, 460, 169 ], "spans": [ { "bbox": [ 88, 157, 460, 169 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 172, 495, 185 ], "type": "text", "angle": 0, "index": 5, "lines": [ { "bbox": [ 89, 172, 493, 185 ], "spans": [ { "bbox": [ 89, 172, 493, 185 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 188, 499, 217 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 89, 189, 500, 201 ], "spans": [ { "bbox": [ 89, 189, 500, 201 ], "type": "text", "content": "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，", "score": 1.0 } ] }, { "bbox": [ 89, 204, 189, 216 ], "spans": [ { "bbox": [ 89, 204, 189, 216 ], "type": "text", "content": "则称为第二范式模式。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 234, 472, 248 ], "type": "text", "angle": 0, "index": 7, "lines": [ { "bbox": [ 88, 234, 473, 248 ], "spans": [ { "bbox": [ 88, 234, 473, 248 ], "type": "text", "content": "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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 250, 504, 310 ], "type": "list", "angle": 0, "index": 11, "blocks": [ { "bbox": [ 93, 250, 456, 263 ], "type": "text", "angle": 0, "index": 8, "lines": [ { "bbox": [ 95, 250, 456, 264 ], "spans": [ { "bbox": [ 95, 250, 456, 264 ], "type": "text", "content": "（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。", "score": 1.0 } ] } ] }, { "bbox": [ 93, 266, 424, 279 ], "type": "text", "angle": 0, "index": 9, "lines": [ { "bbox": [ 95, 266, 425, 280 ], "spans": [ { "bbox": [ 95, 266, 425, 280 ], "type": "text", "content": "（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。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 281, 504, 310 ], "type": "text", "angle": 0, "index": 10, "lines": [ { "bbox": [ 95, 280, 506, 296 ], "spans": [ { "bbox": [ 95, 280, 257, 296 ], "type": "text", "content": "（3）完全函数依赖：设有函数依赖", "score": 1.0 }, { "bbox": [ 257, 282, 285, 294 ], "type": "inline_equation", "content": "{ \\mathsf { W } } { \\to } \\mathsf { A }", "score": 0.88 }, { "bbox": [ 285, 280, 327, 296 ], "type": "text", "content": "，若存在", "score": 1.0 }, { "bbox": [ 327, 281, 354, 295 ], "type": "inline_equation", "content": "\\mathsf { x } \\mathsf { \\subseteq } _ { \\mathsf { W } }", "score": 0.89 }, { "bbox": [ 354, 280, 374, 296 ], "type": "text", "content": "，有", "score": 1.0 }, { "bbox": [ 375, 282, 399, 294 ], "type": "inline_equation", "content": "\\mathsf { X } { \\to } \\mathsf { A }", "score": 0.85 }, { "bbox": [ 399, 280, 465, 296 ], "type": "text", "content": "成立，那么称", "score": 1.0 }, { "bbox": [ 465, 282, 493, 294 ], "type": "inline_equation", "content": "{ \\mathsf { W } } { \\to } \\mathsf { A }", "score": 0.83 }, { "bbox": [ 493, 280, 506, 296 ], "type": "text", "content": "是", "score": 1.0 } ] }, { "bbox": [ 88, 297, 292, 312 ], "spans": [ { "bbox": [ 88, 297, 185, 312 ], "type": "text", "content": "局部依赖，否则就称", "score": 1.0 }, { "bbox": [ 185, 297, 212, 310 ], "type": "inline_equation", "content": "{ \\mathsf { W } } { \\to } \\mathsf { A }", "score": 0.89 }, { "bbox": [ 213, 297, 292, 312 ], "type": "text", "content": "是完全函数依赖。", "score": 1.0 } ] } ] } ], "sub_type": "text" 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"type": "text", "content": "，且 X Y(X 不决定 Y)和 A X(A 不属", "score": 1.0 } ] }, { "bbox": [ 88, 360, 437, 373 ], "spans": [ { "bbox": [ 88, 360, 142, 373 ], "type": "text", "content": "于X)，那么", "score": 1.0 }, { "bbox": [ 143, 360, 166, 372 ], "type": "inline_equation", "content": "\\mathsf { Y } { \\to } \\mathsf { A }", "score": 0.87 }, { "bbox": [ 167, 360, 437, 373 ], "type": "text", "content": "是传递依赖。 Notice:要求非主属性都不传递依赖于候选码。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 390, 451, 403 ], "type": "text", "angle": 0, "index": 14, "lines": [ { "bbox": [ 89, 390, 452, 404 ], "spans": [ { "bbox": [ 89, 390, 452, 404 ], "type": "text", "content": "上一小节例子中student（学号，姓名），study（学号，课程，成绩）都是3NF", "score": 1.0 } ] } ] }, { "bbox": [ 86, 406, 325, 419 ], "type": "text", "angle": 0, "index": 15, "lines": [ { "bbox": [ 88, 407, 326, 421 ], "spans": [ { "bbox": [ 88, 407, 326, 421 ], "type": "text", "content": "这个范式和第三范式有联系，它是 3NF 的改进形式。", "score": 1.0 } ] } ] }, { "bbox": [ 86, 422, 504, 449 ], "type": "text", "angle": 0, "index": 16, "lines": [ { "bbox": [ 89, 422, 505, 434 ], "spans": [ { "bbox": [ 89, 422, 505, 434 ], "type": "text", "content": "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", "score": 1.0 } ] }, { "bbox": [ 88, 436, 142, 451 ], "spans": [ { "bbox": [ 88, 436, 142, 451 ], "type": "text", "content": "BCNF 模式。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 453, 294, 465 ], "type": "text", "angle": 0, "index": 17, "lines": [ { "bbox": [ 88, 453, 295, 467 ], "spans": [ { "bbox": [ 88, 453, 295, 467 ], "type": "text", "content": "四种范式，可以发现它们之间存在如下关系：", "score": 1.0 } ] } ] }, { "bbox": [ 107, 467, 210, 481 ], "type": "interline_equation", "angle": 0, "lines": [ { "bbox": [ 107, 467, 210, 481 ], "spans": [ { "bbox": [ 107, 467, 210, 481 ], "type": "interline_equation", "content": "\\mathrm {B C N F} \\subseteq 3 \\mathrm {N F} \\subseteq 2 \\mathrm {N F} \\subseteq 1 \\mathrm {N F}", "image_path": "1b5eeedcceed3050db4bd32f6b0b831cedb9cf97bd5498c5ab21fd677084b9cf.jpg" } ] } ], "index": 18 }, { "bbox": [ 262, 489, 280, 499 ], "type": "text", "angle": 0, "index": 19, "lines": [ { "bbox": [ 261, 489, 282, 502 ], "spans": [ { "bbox": [ 261, 489, 282, 502 ], "type": "text", "content": "1NF", "score": 1.0 } ] } ] }, { "bbox": [ 282, 512, 476, 524 ], "type": "text", "angle": 0, "index": 20, "lines": [ { "bbox": [ 281, 513, 476, 526 ], "spans": [ { "bbox": [ 281, 513, 292, 526 ], "type": "text", "content": "↓", "score": 1.0 }, { "bbox": [ 317, 513, 476, 525 ], "type": "text", "content": "消去非主属性对码的部分函数依赖", "score": 1.0 } ] } ] }, { "bbox": [ 261, 535, 280, 545 ], "type": "text", "angle": 0, "index": 21, "lines": [ { "bbox": [ 260, 534, 282, 550 ], "spans": [ { "bbox": [ 260, 534, 282, 550 ], "type": "text", "content": "2NF", "score": 1.0 } ] } ] }, { "bbox": [ 282, 558, 476, 571 ], "type": "text", "angle": 0, "index": 22, "lines": [ { "bbox": [ 281, 558, 476, 572 ], "spans": [ { "bbox": [ 281, 558, 292, 572 ], "type": "text", "content": "↓", "score": 1.0 }, { "bbox": [ 317, 559, 476, 572 ], "type": "text", "content": "消去非主属性对码的传递函数依赖", "score": 1.0 } ] } ] }, { "bbox": [ 262, 581, 280, 592 ], "type": "text", "angle": 0, "index": 23, "lines": [ { "bbox": [ 261, 581, 281, 594 ], "spans": [ { "bbox": [ 261, 581, 281, 594 ], "type": "text", "content": "3NF", "score": 1.0 } ] } ] }, { "bbox": [ 282, 604, 465, 617 ], "type": "text", "angle": 0, "index": 24, "lines": [ { "bbox": [ 281, 605, 466, 618 ], "spans": [ { "bbox": [ 281, 605, 293, 618 ], "type": "text", "content": "↓", "score": 1.0 }, { "bbox": [ 317, 605, 466, 618 ], "type": "text", "content": "消去主属性对码的传递函数依赖", "score": 1.0 } ] } ] }, { "bbox": [ 261, 629, 286, 638 ], "type": "text", "angle": 0, "index": 25, "lines": [ { "bbox": [ 260, 627, 287, 641 ], "spans": [ { "bbox": [ 260, 627, 287, 641 ], "type": "text", "content": "BCNF", "score": 1.0 } ] } ] }, { "bbox": [ 87, 648, 129, 660 ], "type": "title", "angle": 0, "index": 26, "lines": [ { "bbox": [ 86, 647, 130, 662 ], "spans": [ { "bbox": [ 86, 647, 130, 662 ], "type": "text", "content": "SQL 语言", "score": 1.0 } ] } ] }, { "bbox": [ 87, 663, 291, 677 ], "type": "title", "angle": 0, "index": 27, "lines": [ { "bbox": [ 88, 661, 292, 679 ], "spans": [ { "bbox": [ 88, 661, 292, 679 ], "type": "text", "content": "数据定义语言 DDL (Data Definition Language)", "score": 1.0 } ] } ] }, { "bbox": [ 88, 679, 409, 723 ], "type": "text", "angle": 0, "index": 28, "lines": [ { "bbox": [ 90, 677, 411, 694 ], "spans": [ { "bbox": [ 90, 677, 411, 694 ], "type": "text", "content": "用于创建、更改或删除数据库对象，如包括定义 Database, Table, View,", "score": 1.0 } ] }, { "bbox": [ 88, 694, 408, 708 ], "spans": [ { "bbox": [ 88, 694, 408, 708 ], "type": "text", "content": "Index,完整性约束条件等，也包括定义对象(RowType行对象, Type列对", "score": 1.0 } ] }, { "bbox": [ 88, 708, 107, 725 ], "spans": [ { "bbox": [ 88, 708, 107, 725 ], "type": "text", "content": "象)", "score": 1.0 } ] } ] }, { "bbox": [ 89, 725, 369, 739 ], "type": "text", "angle": 0, "index": 29, "lines": [ { "bbox": [ 91, 724, 370, 740 ], "spans": [ { "bbox": [ 91, 724, 370, 740 ], "type": "text", "content": "语句包括：CREATE（建立）、ALTER（修改）、DROP（撤销）", "score": 1.0 } ] } ] } ], "discarded_blocks": [ { "bbox": [ 88, 743, 95, 751 ], "type": "page_number", "angle": 0, "index": 30, "lines": [ { "bbox": [ 88, 743, 96, 754 ], "spans": [ { "bbox": [ 88, 743, 96, 754 ], "type": "text", "content": "v", "score": 1.0 } ] } ] } ], "page_size": [ 595, 841 ], "page_idx": 36 }, { "para_blocks": [ { "bbox": [ 87, 79, 309, 92 ], "type": "title", "angle": 0, "index": 0, "lines": [ { "bbox": [ 88, 77, 310, 95 ], "spans": [ { "bbox": [ 88, 77, 310, 95 ], "type": "text", "content": "数据操纵语言 DML (Data Manipulation Language)", "score": 1.0 } ] } ] }, { "bbox": [ 89, 95, 234, 107 ], "type": "text", "angle": 0, "index": 1, "lines": [ { "bbox": [ 90, 92, 236, 111 ], "spans": [ { "bbox": [ 90, 92, 236, 111 ], "type": "text", "content": "用于操纵数据库对象（如表）。", "score": 1.0 } ] } ] }, { "bbox": [ 87, 110, 480, 154 ], "type": "list", "angle": 0, "index": 5, "blocks": [ { "bbox": [ 87, 110, 480, 122 ], "type": "text", "angle": 0, "index": 2, "lines": [ { "bbox": [ 87, 109, 480, 125 ], "spans": [ { "bbox": [ 87, 109, 480, 125 ], "type": "text", "content": "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", "score": 1.0 } ] } ] }, { "bbox": [ 88, 125, 424, 138 ], "type": "text", "angle": 0, "index": 3, "lines": [ { "bbox": [ 88, 126, 423, 139 ], "spans": [ { "bbox": [ 88, 126, 423, 139 ], "type": "text", "content": "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", "score": 1.0 } ] } ] }, { "bbox": [ 88, 142, 382, 154 ], "type": "text", "angle": 0, "index": 4, "lines": [ { "bbox": [ 88, 141, 381, 155 ], "spans": [ { "bbox": [ 88, 141, 381, 155 ], "type": "text", "content": "ü 各种聚集操作，求平均、求和、…等，分组聚集，分组过滤等", "score": 1.0 } ] } ] } ], "sub_type": "text" }, { "bbox": [ 89, 157, 304, 169 ], "type": "text", "angle": 0, "index": 6, "lines": [ { "bbox": [ 91, 157, 305, 172 ], "spans": [ { "bbox": [ 91, 157, 305, 172 ], "type": "text", "content": 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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
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