Trigger is getting mutated

Question

hello gurus ,
i have two tables  MAIN_TB (main table),MAIN_HT (main table history)
MAIN_TB CONSIST OF
C_CODE  VARCHAR2;
OCC_NO NUMBER;
can_cont  char(1);
CONT_NO VARCHAR2;
LOG  OB_LOG;
AND
MAIN_HT CONSIST OF
HT_OCC_NO  NUMBER;
C_CODE  VARCHAR2
OCC_NO NUMBER;
can_cont char(1);
CONT_NO VARCHAR2;
LOG  OB_LOG;now my condition is this the HT table should get inserted whenever the occ_no in TB is updated when can_cont of TB table isnull and HT table should not be inserted when can_cont of TB is not null; but when i try this my trigger starts mutating how to stop that is there any other way that i cud use to develop my trigger
my trigger is
CREATE OR REPLACE TRIGGER main_tr
   AFTER INSERT OR UPDATE OF occ_no
   ON main_tb
   REFERENCING NEW AS NEW OLD AS OLD
   FOR EACH ROW
DECLARE
   ht_occ_no      NUMBER := 0;
   no_of_update   NUMBER := 0;
BEGIN
   BEGIN
      SELECT MAX (nvl (ht_occ_no, 0))
        INTO ht_occ_no
        FROM main_ht
       WHERE c_code = :NEW.c_code AND cont_no = :NEW.cont_no;
   EXCEPTION
      WHEN OTHERS
      THEN
         raise_application_error
                         (-20001,
                             'Error While Inserting Into MAIN_ht  In MAIN_TR'
                          || SQLERRM
   END;
   BEGIN
      SELECT mtb.LOG.no_of_update
        INTO no_of_update
        FROM main_tb mtb
       WHERE mtb.c_code = :OLD.c_code
         AND mtb.cont_no = :OLD.cont_no
         AND mtb.can_cont IS NULL;
   EXCEPTION
      WHEN NO_DATA_FOUND
      THEN
         no_of_update := 0;
   END;
   IF UPDATING
   THEN
      IF no_of_update = 0
      THEN
         ht_occ_no := ht_occ_no + 1;
      END IF;
   END IF;
   IF INSERTING
   THEN
      IF no_of_update = 0
      THEN
         RETURN;
      END IF;
   END IF;
   BEGIN
      INSERT INTO main_ht
                  (ht_occ_no, c_code, occ_no, can_cont, cont_no, LOG
           VALUES (ht_occ_no, :OLD.c_code:OLD.occ_no, can_cont, cont_no, LOG
   EXCEPTION
      WHEN OTHERS
      THEN
         raise_application_error
                         (-20001,
                             'Error While Inserting Into MAIN_ht  In MAIN_TR'
                          || SQLERRM
   END;
END main_tr;
/how do i stop trigger from mutating and how do i get my result with out using pragma autonomus transaction ?
thanks and Regards,
friend
Edited by: most wanted!!!! on Feb 5, 2012 10:49 PM

Answer 1

i ll check
actually my data should be like
1'st
Main TB
c_code  cont_no  occ_no  can_cont   log
c1          111         1          n             0
then
Main HT
ht_occ_no  c_code  cont_no  occ_no  can_cont   log
should be empty
when
Main TBc_code cont_no occ_no can_cont log
c1 111 2 n 1
occ_no is updated
then
Main HT
ht_occ_no c_code cont_no occ_no can_cont log
1 c1 111 1 n 0
and after occ_no changes to 3 times for main tb
Main TB
c_code  cont_no  occ_no  can_cont   log
c1          111         5          n             1
then
then
Main HT
ht_occ_no c_code  cont_no  occ_no  can_cont   log
1                c1         111        1           n              0
1                c1         111        2           n              1
1                c1         111        3           n              2
1                c1         111        4           n              3
when can_cont is 'Y' then
Main TBc_code cont_no occ_no can_cont log
c1 111 5 y 1
no insert should take place in main_ht
then
Main HT
ht_occ_no c_code cont_no occ_no can_cont log
1 c1 111 1 n 0
1 c1 111 2 n 1
1 c1 111 3 n 2
1 c1 111 4 n 3
when
once again the same data is inserted in main tb then
Main TB
c_code  cont_no  occ_no  can_cont   log
c1          111         5          y             1
c1          111         1          y             0
then
Main HT
ht_occ_no c_code  cont_no  occ_no  can_cont   log
1                c1         111        1           n              0
1                c1         111        2           n              1
1                c1         111        3           n              2
1                c1         111        4           n              3
nothing should hapen first time
second time when updated then
Main TBc_code cont_no occ_no can_cont log
c1 111 5 y 1
c1 111 2 y 1
then
Main HT
ht_occ_no c_code cont_no occ_no can_cont log
1 c1 111 1 n 0
1 c1 111 2 n 1
1 c1 111 3 n 2
1 c1 111 4 n 3
2 c1 111 1 n 0
nothing should hapen first time
this is wat i want pheww..Edited by: most wanted!!!! on Feb 6, 2012 3:31 AM
Edited by: most wanted!!!! on Feb 6, 2012 3:44 AM