dating haram - Validating constraints and oracle
Although the typical constraint in an operational system is both enabled and validated, any constraint could be validated but not enabled or vice versa (enabled but not validated). In some cases, you will know that the conditions for a given constraint are true, so you do not need to validate or enforce the constraint.
However, you may wish for the constraint to be present anyway to improve query optimization and performance.
In order to use a constraint for enforcement, the constraint must be in the ENABLE state.
An enabled constraint ensures that all data modifications upon a given table (or tables) satisfy the conditions of the constraints.
DROP Constraint command Drop an integrity constraint.
Syntax: DROP PRIMARY KEY [CASCADE] DROP UNIQUE column [CASCADE] DROP CONSTRAINT constraint_name 'Column' can be either a single column name or several columns separated with commas, - DISABLE allow incoming data, regardless of whether it conforms to the constraint - VALIDATE ensure that existing data conforms to the constraint - NOVALIDATE existing data does not have to conform to the constraint These can be used in combination DISABLE - DISABLE NOVALIDATE is the same as DISABLE.
Data modification operations which produce data that violates the constraint fail with a constraint violation error.