Update Operations on Relations

Integrity constraints should not be violated by the update operations. Several update operations may have to be grouped together. Updates may propagate to cause other updates automatically. This may be necessary to maintain integrity constraints. In case of integrity violation, several actions can be taken:
1. Cancel the operation that causes the violation (REJECT option)
2. Perform the operation but inform the user of the violation
3. Trigger additional updates so the violation is corrected (CASCADE option, SET NULL option)

4. Execute a user-specified error-correction routine