| 摘要 |
A method, computer program, and database system are disclosed for executing database queries. The database includes a first table (T 1 ) having a primary key (PK) column and a first correlated value column (CV 1 ) and a second table (T 2 ) having a foreign key (FK) column related to the primary key column of the first table and a second correlated value column (CV 2 ). One implementation of the method includes preparing a database query for execution based at least in part on application of a derived constraint rule (DCR) having the form, (PK=FK)->CV<SUB>2</SUB>+C<SUB>1</SUB><=CV<SUB>1</SUB><=CV<SUB>2</SUB>+C<SUB>2</SUB>, where C<SUB>1 </SUB>and C<SUB>2 </SUB>are constants and "->" means "implies," to produce an execution plan. Abort steps that are conditioned on changes in the DCR are also included in the execution plan. The plan is then executed.
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