Method of optimizing a query having an existi subquery and a not-exists subquery

摘要

For SQL query, program storage device storage optimization program is provided for Optimizing Queries for a kind of optimisation technique. It includes & ldquo that whether it includes WHERE clause that inquiry is analyzed to determine it; EXISTS” With a Ge & ldquo subqueries; NOT EXISTS” Subquery, EXISTS-equivalent subqueries, Boolean factor. Two subqueries of test are carried out if it is, sorting out. Then, compensation predicate is applied to one of them, to carry out QGM conversion queries. One sub- query block is stacked on another subquery block, to eliminate a subquery. The process allows more efficiently transformed query to carry out than original query, while providing identical result. Then the inquiry executes the relational database from above-mentioned in order to efficient retrieval data in a computer.