Exploitation of uniqueness properties using a 1-tuple condition for the optimization of SQL queries
US5615361A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 7, 1995 |
| Grant date | Mar 25, 1997 |
| Priority date | — |
| Expiry date | Feb 7, 2015 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S707/99933
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The present invention optimizes SQL queries by exploiting uniqueness properties. In identifying whether the generalized 1-tuple condition exists, the query is first analyzed to determine whether any columns referenced in a predicate of the query are bound. According to the present invention, columns may be bound to constant values or correlated columns or columns that are already bound. The bound columns, if any, are then analyzed to determine whether any of the bound columns comprise a key for its associated table. If these conditions exist, then the query satisfies the 1-tuple condition, in that it returns at most one tuple. Once the generalized 1-tuple condition has been identified to exist for the query, important query transformations can be performed for optimization purposes. These query transformations comprise the transformation of scalar subqueries into joins, or the elimination of distinctiveness requirements (i.e., DISTINCT keywords) from SELECT clauses.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.