UPDATE使用ROWID或ROWNUM

Question

I want to update CAR_CASE from CAR when I add a new row in HIRE used trigger

create or replace TRIGGER HIRE_CAR_CASE_UPDATE 
AFTER INSERT OR UPDATE OF CAR_ID ON HIRE 
REFERENCING OLD AS OLD NEW AS NEW 

BEGIN
UPDATE CAR SET CAR_CASE =
(SELECT HIRE.CAR_CASE FROM HIRE where HIRE.CAR_ID = CAR.CAR_ID and TO_DATE (HIRE.DATE_) = TO_DATE(sysdate))
WHERE rowid = :NEW.ROWID;

END;

Answer 1

It appears that what you wanted to do was

CREATE OR REPLACE TRIGGER HIRE_CAR_CASE_UPDATE 
  AFTER INSERT OR UPDATE OF CAR_ID ON HIRE 
  FOR EACH ROW
BEGIN
  UPDATE CAR c
    SET c.CAR_CASE = :NEW.CAR_CASE
    WHERE c.CAR_ID = :NEW.CAR_ID;
END HIRE_CAR_CASE_UPDATE;

Because I don't know what your database looks like or how it's to be used I can't say if a similar update should be made to the "old" CAR referred to by :OLD.CAR_ID.

Perhaps more to the point, however - this is business logic which really should not be implemented in a trigger. Put this kind of logic in your application, or perhaps put it into a stored procedure which performs all the necessary logic for a particular business task, rather than scattering logic willy-nilly among a bunch of triggers, procedures, individual SQL statements, etc.

Best of luck.