Constraint states

 

A file can be in several constraint states.

• Non-constraint relationship state. No referential constraint exists for a file in this state. If a constraint relationship once existed for the file, all information about it has been removed.

• Defined state. A constraint relationship is defined between a dependent and a parent file. It is not necessary to create the member in either file to define a constraint relationship. In the defined state, the constraint can be:

  • Defined and enabled. A defined and enabled constraint relationship is for definition purposes only. The rules for the constraint are not enforced. A constraint in this state remains enabled when it goes to the established state.

  • Defined and disabled. A defined constraint relationship that is disabled is for definition purposes only. The rules for the constraint are not enforced. A constraint in this state remains disabled when it goes to the established state.

• Established state. The dependent file has a constraint relationship with the parent file. A constraint will be established only if the attributes match between the foreign and parent key. Members must exist for both files. In the established state, the constraint can be:

  • Established and enabled. An established constraint relationship that is enabled causes the database to enforce referential integrity.

  • Established and disabled. An established constraint relationship that is disabled directs the database to not enforce referential integrity.

 

Parent topic:

Ensuring data integrity with referential constraints