constraint error message

hi!

i have this pl/sql constraint testing program :

CREATE OR REPLACE TRIGGER emp_del_trig
BEFORE DELETE ON emp FOR EACH ROW
DECLARE
  dummy INTEGER;
BEGIN
  DBMS_OUTPUT.PUT_LINE('old.deptno :' || :old.deptno);   IF DELETING THEN
    SELECT COUNT(*) INTO dummy FROM emp WHERE deptno = :old.deptno;     DBMS_OUTPUT.PUT_LINE('value :' || dummy || ' old.deptno :' || :old.deptno);

    IF dummy < 3 THEN raise_application_error( -20001, 'May not lower number of employees in this dept');

    END IF;
  END IF;
END; but when I do the following statement I get error messages : DELETE FROM emp WHERE deptno=10;

old.deptno :10
DELETE FROM emp WHERE deptno=10
*
ERROR at line 1:

ORA-04091: table IFS49.EMP is mutating, trigger/function may not see it
ORA-06512: at "IFS49.EMP_DEL_TRIG", line 6
ORA-04088: error during execution of trigger 'IFS49.EMP_DEL_TRIG'

old.deptno :10

What I am doing wrong? Thank you very much for any help. I am an oracle newbie and I am quite clueless on what's going on.

Ciao,
Michele Received on Mon Nov 15 1999 - 17:49:01 CST