Foreign key enforcement
The rules that you specify for a referential constraint apply to parent key changes. The database enforces a no-action rule on the insert and update operations on the foreign key to ensure that the value of every non-null foreign key matches the value of the parent key.
The system returns a referential constraint violation if a matching parent key does not exist for the new foreign key value, and does not insert or update the dependent record.
Parent topic:
Referential integrity enforcement