Possible operations with constraints as
follows.
Ø Enable
Ø Disable
Ø Enforce
Ø Drop
ENABLE
This will enable the constraint. Before
enable, the constraint will check the existing data.
Ex:
SQL> alter table student12
enable constraint un;
DISABLE
This will disable the constraint.
Ex:
SQL> alter table student12
disable constraint un;
ENFORCE
This will enforce the constraint rather than
enable for future inserts or updates.
This will not check for existing data while
enforcing data.
Ex:
SQL> alter table student12
enforce constraint un;
DROP
This will remove the constraint.
Ex:
SQL> alter table student12
drop constraint un;
Once the table is dropped, constraints
automatically will drop.
