testing variable state in functions

HI,

I've got a simple function which has a pb when I test the r_serial_n variable. It seems that ( see below ) (1)IF is not taken in account. It returns a blank result. If the statement reaches ELSE, it works ..

It seems that NULL statement is not suitable here, but what else may I use ?

Thanks

CREATE OR REPLACE FUNCTION warr_date (f_serial_n VARCHAR2) RETURN DATE
IS
r_serial_n VARCHAR2(20) ;
i_arrival DATE;
BEGIN
SELECT serial_n
INTO r_serial_n
FROM RMA_R
WHERE serial_n = f_serial_n;

SELECT arrival
INTO i_arrival
FROM INFOGLOB
WHERE serial_n= f_serial_n;

(1) IF r_serial_n IS NULL THEN

RETURN(i_arrival);
(2)ELSE

RETURN(r_warr_date(f_serial_n));
END IF; EXCEPTION
  WHEN NO_DATA_FOUND THEN RETURN(NULL);
END;
/ Received on Mon Jan 07 2002 - 10:13:24 CST