Oracle functions issue

Question

I am facing a strange problem with Functions. I am creating a function to achieve one of my requirement. please have a look on below problem explanation
I have created below table
CREATE TABLE APPS.XX_CHECK_MAIL
CHECK_NUMBER NUMBER,
MAIL_STATUS VARCHAR2(50 BYTE),
VOID_MAIL_STATUS VARCHAR2(50 BYTE)
And i wrote the below function to insert values ..
CREATE OR REPLACE FUNCTION XX_CHECK_FUN1(X_CHECK_NUMBER1 NUMBER)
RETURN NUMBER
IS
V_NUMBER1 NUMBER(10);
A NUMBER (10);
BEGIN
SELECT CHECK_NUMBER INTO A FROM XX_CHECK_MAIL WHERE CHECK_NUMBER = X_CHECK_NUMBER1;
IF A IS NULL THEN
INSERT INTO XX_CHECK_MAIL VALUES (X_CHECK_NUMBER1,'Y','N');
V_NUMBER1:=1;
COMMIT;
END IF;
RETURN V_NUMBER1;
END;
So My intention was before insert into a table I want to check the check_number is existed in the same table or not
the above function was created successfully but when i am running the same with below query
SELECT XX_CHECK_FUN1(1300) FROM DUAL;
its not returning any value and the records are not inserted.

Answer 1

Won't work for two reasons :
1. The select inside the procedure will raise an exception (not handled) when no data found
2. You can't execute DMLs inside queries.
Try something like this :SQL> CREATE OR REPLACE FUNCTION XX_CHECK_FUN1(X_CHECK_NUMBER1 NUMBER)
  2     RETURN NUMBER
  3  IS
  4     V_NUMBER1 NUMBER(10);
  5     A NUMBER (10);
  6  BEGIN
  7     SELECT CHECK_NUMBER INTO A FROM XX_CHECK_MAIL
  8     WHERE CHECK_NUMBER = X_CHECK_NUMBER1;
  9     return(0);
10  exception
11     when no_data_found then
12     INSERT INTO XX_CHECK_MAIL VALUES (X_CHECK_NUMBER1,'Y','N');
13     V_NUMBER1:=1;
14     COMMIT;
15     RETURN V_NUMBER1;
16* END;
SQL> /
Function created.
SQL> SELECT XX_CHECK_FUN1(1300) FROM DUAL;
SELECT XX_CHECK_FUN1(1300) FROM DUAL
ERROR at line 1:
ORA-14551: cannot perform a DML operation inside a query
ORA-06512: at "TEST.XX_CHECK_FUN1", line 12
ORA-01403: no data found
SQL> var I number;
SQL> exec :I := XX_CHECK_FUN1(1300);
PL/SQL procedure successfully completed.
SQL> print I
         I
         1
SQL> select * from XX_CHECK_MAIL;
CHECK_NUMBER MAIL_STATUS
VOID_MAIL_STATUS
        1300 Y
N
SQL> exec :I := XX_CHECK_FUN1(1300);
PL/SQL procedure successfully completed.
SQL> print I
         I
         0
SQL> select * from XX_CHECK_MAIL;
CHECK_NUMBER MAIL_STATUS
VOID_MAIL_STATUS
        1300 Y
N
SQL> exec :I := XX_CHECK_FUN1(1400);
PL/SQL procedure successfully completed.
SQL> print I
         I
         1
SQL> select * from XX_CHECK_MAIL;
CHECK_NUMBER MAIL_STATUS
VOID_MAIL_STATUS
        1300 Y
N
        1400 Y
N
SQL>