Question

I need to create a trigger that writes changes in a shadow table. I know how to create the trigger but my challenge is that I need the records in the new table to exist even after a rollback.

This is an example of how the output will look like

INSERT INTO department VALUES (95, 'PURCHASING', 'CHICAGO');<br>
ROLLBACK;

1 rows inserted.
rollback complete.

SELECT * FROM department_log;

DEPARTMENT_ID           DEPARTMENT_NAME       ADDRESS               OPERATION_TIME            
---------------------- -------------------- -------------------- ------------------ 
90                      HR                    CHICAGO               03-NOV-11
95                      PURCHASING            CHICAGO               03-NOV-11

SELECT * from department WHERE department_id >= 90;

DEPARTMENT_ID           DEPARTMENT_NAME       ADDRESS              
---------------------- -------------------- -------------------- 
90                      HR                    CHICAGO

Answer 1

You’ll need to use autonomous transactions.

SQL> create table t (col1 number);

Table created.

SQL> create table t_shadow( col1 number, dt date );

Table created.

SQL> create trigger trg_t
  2    before insert on t
  3    for each row
  4  declare
  5    pragma autonomous_transaction;
  6  begin
  7    insert into t_shadow( col1, dt )
  8      values( :new.col1, sysdate );
  9    commit;
 10  end;
 11  /

Trigger created.

SQL> insert into t values( 1 );

1 row created.

SQL> rollback;

Rollback complete.

SQL> select * from t;

no rows selected

SQL> select * from t_shadow;

      COL1 DT
---------- ---------
         1 09-NOV-11

Note that if you find yourself using autonomous transactions for anything other than persistent logging, you are almost certainly doing something wrong. Autonomous transactions are a very dangerous and very frequently misused feature.