Meaning: If you are deleting a record in the master table , how should it react if it has got transaction records
4 type of delete actions
None – IT WILL DELETE MASTER RECORDS AND WILL NOT DELETE CHILD RECORDS
Cascade – IT WILL FIRST DELETE THE CHILD RECORDS AND COME BACK AND DELETES THE MASTER RECORD
Restricted- IT WILL NOT DELETE ANY OF THE RECORDS [MASTER AND CHILD] – IT WILL THROW A WARNING MESSAGE – TRANSACTIONS EXISTS IN XYZ TABLE.CANNOT DELETE THE RECORD.
C + R [Cascade + restricted] – OPTION IS LEFT TO THE USER TO DELETE OR NOT
Note: Delete actions should be always be set on Master table