发明名称 |
REDUNDANT JOIN ELIMINATION AND SUB-QUERY ELIMINATION USING SUBSUMPTION |
摘要 |
A query rewrite optimization method for eliminating a redundant join and equivalent subquery in an SQL query before generation and selection of the optimal quer y execution plan. The method evaluates a query for a particular join of a first and second quantifier each ranging over the same table. A determination is made whether the row set produced relative to the second quantifier subsumes the row set produced relative to the first quantifier. The query ma y be reformed to eliminate the join and the second quantifier. A further determination of the removability of the second quantifier may be required such as by evaluating a of a cardinality constraint when query output cardinality is material.
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申请公布号 |
CA2374271(A1) |
申请公布日期 |
2003.09.01 |
申请号 |
CA20022374271 |
申请日期 |
2002.03.01 |
申请人 |
IBM CANADA LIMITED-IBM CANADA LIMITEE |
发明人 |
KOO, FRED;LEUNG, TING Y. |
分类号 |
G06F17/30;(IPC1-7):G06F17/30 |
主分类号 |
G06F17/30 |
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