Each constraint has two additional
attributes to support deferred checking of constraints.
Ø Deferred
initially immediate
Ø Deferred
initially deferred
Deferred initially immediate checks for
constraint violation at the time of insert.
Deferred initially deferred checks for
constraint violation at the time of commit.
Ex:
SQL> create table student12(no
number(2), name varchar(10), marks number(3),
constraint un unique(no) deferred initially immediate);
SQL> create table student12(no
number(2), name varchar(10), marks number(3),
constraint un unique(no) deferred initially deferred);
SQL> alter table student12
add constraint un unique(no) deferrable initially deferred;
SQL> set constraints all immediate;
This will enable all the constraints violations at the time of inserting.
SQL> set constraints all deferred;
This will enable all the constraints violations at the time of commit.
