Having problem with trigger.(help needed)

Question

HI all,
i m totally new to the PL/SQL.... hope someone can help me with this.....
i am now using trigger to block inserting into "attendance99" table when the record reach the maximum limit and insert the record to the "waiting_list" table.
The problem i face is by using RAISE_APPLICATION_ERROR, it will block the insertion to the "waiting_list" table as well.....
i had try to use only DBMS_OUTPUT.PUT_LINE instead but end up >>> inserting record into both table "attendance" and "waiting_list" tables.
CREATE OR REPLACE TRIGGER trig_attendance
Before insert on attendance99
referencing new as new
for each row
DECLARE
maxstud NUMBER(2);
currstud NUMBER(2);
Begin
SELECT COUNT(*) INTO currstud FROM attendance99 WHERE offering_id=:New.offering_id;
SELECT max_no_students INTO maxstud FROM offering WHERE offering_id=:New.offering_id;
IF currstud >= maxstud
THEN
insert_waitinglist(:New.offering_id, :New.student_id, :New.evaluation, :New.amount_paid);
RAISE_APPLICATION_ERROR (-20500, 'Sorry, this Offering ID has reach maximum students, you will be placed into waiting list!');
END IF;
END;
CREATE OR REPLACE PROCEDURE insert_waitinglist
(v_offeringid IN waiting_list.offering_id%TYPE,
v_studentid IN waiting_list.student_id%TYPE,
v_evaluation IN waiting_list.evaluation%TYPE,
v_amountpaid IN waiting_list.amount_paid%TYPE)
IS
BEGIN
     INSERT INTO waiting_list (offering_id, student_id, evaluation, amount_paid)
VALUES (v_offeringid, v_studentid, v_evaluation, v_amountpaid);
END insert_waitinglist;
-----------------------------------------------

Answer 1

SQL> create table a (x number);
Table created.
SQL> create table b (x number);
Table created.
SQL> ed
Wrote file afiedt.buf
  1  create or replace procedure insert_b(x in number) is
  2    pragma autonomous_transaction;
  3  begin
  4    insert into b values (x);
  5    commit;
  6* end;
SQL> /
Procedure created.
SQL> ed
Wrote file afiedt.buf
  1  create or replace trigger trig_a
  2  before insert on a
  3  for each row
  4  declare
  5    v_cnt NUMBER;
  6  begin
  7    select count(*) into v_cnt from a;
  8    if v_cnt >= 5 then
  9      insert_b(:new.x);
10      raise_application_error(-20500, 'Limit exceeed.  Inserted to B instead');
11    end if;
12* end;
13  /
Trigger created.
SQL> insert into a values (1);
1 row created.
SQL> insert into a values (2);
1 row created.
SQL> insert into a values (3);
1 row created.
SQL> insert into a values (4);
1 row created.
SQL> insert into a values (5);
1 row created.
SQL> insert into a values (6);
insert into a values (6)
ERROR at line 1:
ORA-20500: Limit exceeed.  Inserted to B instead
ORA-06512: at "SCOTT.TRIG_A", line 7
ORA-04088: error during execution of trigger 'SCOTT.TRIG_A'
SQL> select * from a;
         X
         1
         2
         3
         4
         5
SQL> select * from b;
         X
         6
SQL>