关系表达式的一些属性

ACM-SE 17 Pub Date : 1979-04-09 DOI:10.1145/503506.503525

Martin K. Solomon

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引用次数: 8

摘要

在关系型(微积分和代数)数据库子语言中，我们得到了表达式的威力的一些结果。我们的主要结果说明了关系表达式的等价和有限等价问题的不可判定性。我们还观察到，关系代数中使用的连接类型会影响该代数问题的复杂性。例如，使用相等连接而不是自然连接会导致不必要的复杂表达式。我们将这些结果与查询优化和并发控制问题联系起来。

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Some properties of relational expressions

We obtain certain results concerning the power of expressions in relational (calculus and algebra) database sublanguages. Our main results state the undecidability of the equivalence and finite equivalence problems for relational expressions. We also observe that the type of join used in a relational algebra affects the complexity of problems for that algebra. For example, using equi-joins instead of natural joins leads to unnecessarily complex expressions. We relate these results to the problems of query optimization and concurrency control.

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ACM-SE 17

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