The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 04, 2003
Filed:
Feb. 17, 2000
Ting Yu Leung, San Jose, CA (US);
Tuong Chanh Truong, San Jose, CA (US);
Monica Sachiye Urata, Saratoga, CA (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
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 the WHERE clause which contains an “EXISTS” subquery and a “NOT EXISTS” subquery, or EXISTS-equivalent subqueries, in Boolean factor. If so, the subsumption test is performed on two subqueries. Then, the compensation predicate is applied to one of them, to perform the QGM transformation of the query. One subquery block is stacked on top of the other subquery block, in order to eliminate one subquery. This procedure allows the transformed query to perform more efficiently than the original query while providing same results. The query is then executed in the computer to efficiently retrieve data from the relational database.