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Method of optimizing SQL queries where a predicate matches nullable operands
Method of optimizing SQL queries where a predicate matches nullable operands
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机译:谓词与可为空的操作数匹配的SQL查询的优化方法
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摘要
An optimization technique for SQL queries, a program storage device storing the optimization program, and an apparatus for optimizing a query is provided. A query is analyzed to determine whether it includes a predicate for matching nullable operands and, if so, it is transformed to return TRUE when all operands are NULLs. If the DBMS supports this new function, the predicate is marked. If not, the predicate is re-written into a CASE expression having two SELECT clauses. The query is then executed in the computer to efficiently retrieve data from the relational database.
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