VIEWS:

            CREATE VIEW CVIEW(VCNO,VCNAME,VCLOC) AS

                           (SELECT CNO,CNAME,CLOC FROM CUST WHERE

                                                                                       CNAME LIKE “%X%)

Ø  Logical representation of the table

Ø  Stored in virtual memory

Ø  Can be derived from single table or multiple tables

Ø  Views are updateable if they are derived from single table without any column functions , group by

Ø  Multiple views can be generated from single table.

Ø  Views are stored in sysviews

Advantages of Views:

Ø  Data security

Ø  Data correctness

Ø  Logical data independence

Ø  Part of the information can be visible to the sers

Ø  Accessing can be faster.

DELETE RULES:

Ø  Delete rules can be applied for delete command against Database.

Ø  Delete rules are 3 types

1.      on delete cascade – all matching child rows will be deleted automatically when we delete parent row.

2.      on delete restrict – all matching rows will be restricted when we delete parent row which is default.

3.      on delete set null – all matching child row will be set to null when we delete parent row.