Problems changing the date with a trigger in oracle

Question

I want to create a trigger that can modify or insert a date in my table \"contracts\":

\"If a client with a current contract signs a new one, the end date Of the previou

Answer 1

You want something like this:

CREATE OR REPLACE TRIGGER TRIGGER_D
BEFORE
INSERT OR UPDATE ON CONTRACTS
FOR EACH ROW
DECLARE
BEGIN
  UPDATE CONTRACTS
  SET    ENDDATE   = :NEW.STARTDATE - INTERVAL '1' DAY
  WHERE  CLIENTID  = :NEW.CLIENTID
  AND    ENDDATE   > :NEW.STARTDATE
  AND    STARTDATE < :NEW.STARTDATE;
END;

However, it is updating the table that the trigger is monitoring and it seems likely that the trigger will cause updates that will invoke the trigger again and get a mutating table error.

You might be better to wrap your business logic in a stored procedure where it can perform the update on the previous rows and then do the insert/update. Then, rather than performing DML statements directly on the table instead invoke the stored procedure.