Database's foreign key!

The foreign key is very importent in db designing.

Recently test my firebird db system, I used IB Expert create a table and set up some fields, type and primary key.

After I set Constraints->Foreign keys-> Set default rule->On Field, FK Table, FK Field etc.

"Update Rule" and "Delete Rule"is very interesting.

You can set: NO ACTION, CASCADE, SET NULL and SET DEFAULT. It not like MySQL after setup rule but can not used. Is very nice!