ROLLBACK

USING ROLLBACK: - ROLLBACK is an opposite to COMMITT. It will undo the operation that we perform on database that is not yet committed.

Syntax: - ROLLBACK

We explicitly ROLLBACK the transaction if we wanted to revert any DML operation that occurred on the database.

Example for System ROLLBACK: While Work is under process, if suddenly power goes then oracle will ROLLBACK the transaction.

Ex: - First we are updating the record shown below

SQL> update EMP set sal=sal+1000 where ename='JOHN';

  -- 1 updated

Now we will retrieve the record which we have updated by using SELECT Command shown below

SQL> select *from EMP where ename='JOHN';

EMPNO ENAME          JOB            MGR    HIREDATE        SAL      COMM    DEPTNO

 7125    SURESH        ANALYST     7902    22-DEC-82     16000      1000        20

Now if we ROLLBACK then we can see below result

SQL> ROLLBACK;

Rollback complete.

Then again retrieving the record what we have updated by using SELECT command

SQL> select *from EMP where ename='JOHN';

EMPNO ENAME                JOB             MGR   HIREDATE        SAL      COMM    DEPTNO

--------- -------------------- --------- --------- --------- --------- --------- ---------

7125     SURESH               ANALYST    7902   22-DEC-82     15000      1000        20

Here we can see it is Rollback (Sal from 16000 to 15000).