| 摘要 |
A method, database system and computer program are disclosed for optimizing a SQL query, in which the SQL query includes a WHERE clause and a FROM clause. An evaluation is done to determine whether a non-covering join index partially but not completely covers the query. If it does, the join index is added to the FROM clause of the query without removing the partially covered base tables and the WHERE clause of the query is modified by: (1) mapping a query condition to the join index for its partially covered base tables; and (2) adding a join back condition from the join index to a base table from which the join index was formed.
|
