Question

Create a trigger to compute the value of the duration column when a tuple is inserted in ContractInfo .

ContractInfo Table
HAS_CONTRACT          DATE_FROM DATE_TO     DURATION
--------------------- --------- --------- ----------
Simon Palm            20-AUG-01 19-AUG-02          0
Simon Palm            20-SEP-02 19-AUG-03          0
Flut                  10-JUN-99 09-SEP-02          0

How can I make a trigger? I am a bit confused with the trigger.

Answer 1

SQL> create or replace trigger ContractInfo_buifer
  2  before insert or update on contractinfo
  3  for each row
  4  declare
  5  begin
  6    :new.duration := :new.date_to - :new.date_from; -- answer in days.
  7  END;
  8  /

Trigger created.

SQL> insert into ContractInfo (HAS_CONTRACT,  DATE_FROM, DATE_TO ) values ('Simon Palm', to_date('20-AUG-01', 'dd-mon-rr'), to_date('19-AUG-02', 'dd-mon-rr'))
  2  /

1 row created.

SQL> select * from contractinfo;

HAS_CONTRA DATE_FROM DATE_TO     DURATION
---------- --------- --------- ----------
Simon Palm 20-AUG-01 19-AUG-02        364