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数据库系统概论5版2016chp09概要
第三篇 系统篇;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;2. 查询检查 ;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;选择操作的实现(续);An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;An Introduction to Database System;2. 连接、笛卡尔积的结合律
设E1,E2,E3是关系代数表达式,F1和F2是连接运算的条件,则有
(E1 × E2) × E3≡E1 × (E2 × E3)
(E1 E2) E3≡E1 (E2 E3)
(E1 E2) E3≡E1 (E2 E3) ;4. 选择的串接定律
( (E)) ≡ (E)
这里,E是关系代数表达式,F1、F2是选择条件。
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