Avoid an insertion in a table

Question

Good morning!!
I'm trying to create a trigger in order to avoid some undesiderable insertions in a table of my DB. I check some basic rules of the data and I would like that in some cases the insertion won't be committed, but if I use a raise_application_error in my trigger, an error appears informing me that the number of the exception is out of range, and I can't make a rollback inside the trigger.
I've tried to insert the wrong data in other table and program other after insert trigger on this auxiliary table to drop the incorrect data, but without possitive result. The code of both triggers is as follow:
-- Table where I want to avoid the insertions: TABLE1
-- Auxiliar table: TABLE_AUX
CREATE OR REPLACE TRIGGER CHECK_CONDITIONS
AFTER INSERT
ON TABLE1
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
DECLARE
EXISTE NUMBER;
PREV_DATA1 NUMBER;
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
SELECT COUNT(*),DATA1 INTO EXISTE,PREV_DATA FROM TABLE1 WHERE DATA2 = :NEW.DATA2 GROUP BY DATA1;
IF EXISTE = 1 THEN
dbms_output.put_line('Mother Word '||:new.mother_word ||' existente en BD');
IF PREV_DATA <> :NEW.DATA1 THEN
     INSERT INTO TABLE_AUX VALUES(:NEW.DATA1,:NEW.DATA2);
     COMMIT;
     END IF;
END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN NULL;
WHEN OTHERS THEN
     dbms_output.put_line(to_char(sqlcode)||': '||to_char(sqlerrm));
END CHECK_CONDITIONS;
CREATE OR REPLACE TRIGGER DELETE_BAD_DATA
AFTER INSERT
ON TABLE_AUX
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
DELETE FROM TABLE1 WHERE DATA1 = :NEW.DATA1 AND DATA2 = :NEW.DATA2;
COMMIT;
EXCEPTION
WHEN OTHERS THEN
     dbms_output.put_line(to_char(sqlcode)||to_char(sqlerrm));
END DELETE_BAD_DATA;
Any help would be useful.
Thanks in advance.
Isabel

Answer 1

One thing if you want to do a rollback or commit inside a trigger is using autonomous transaction inside a trigger..Please find the sample code for that which might be useful in your case
CREATE OR REPLACE TRIGGER t_autonomous_tx
BEFORE INSERT
ON person
DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
INSERT INTO audit_log
(chng_when, commentcol)
VALUES
(SYSDATE, 'Reporting an error');
COMMIT;
END t_autonomous_tx;