Update Rules in SQL – SQL Server Tutorial

UPDATE RULES  :-

The different update rules are

• On  update no action
• On update cascade
• On update set null
• On update set default

The update rules specifies how child record is effected if primary key of the parent record is updated.

(i) on update no action :-

• Parent can’t be updated it matching child record exists.

(ii) on update cascade :-

• If the foreign key is declared with or update cascade then if primary key is updated matching foreign key also is updated automatically.

(iii) on update set null :-

• The foreign key declared with on update set null then if primary key is updated the matching foreign key value set to null.

(iv) on update set default :-

• If primery key is updated do matching foreign key value set to default value