Ensuring Data Integrity in Tables

To ensure that the data in your tables satisfies the business rules that your application models, you can use constraints, application logic, or both.

Constraints restrict the values that columns can have. Trying to change the data in a way that violates a constraint causes an error and rolls back the change. Trying to add a constraint to a populated table causes an error if existing data violates the constraint.

Constraints can be enabled and disabled. By default, they are created in the enabled state.

This section contains:

• About Constraint Types

• Tutorial: Adding Constraints to Existing Tables