Factorial function(DB)

CREATE OR REPLACE FUNCTION factorial(
                     p_n NUMBER
                    )
  RETURN NUMBER
  IS
  BEGIN
      IF p_n =1
        THEN
          RETURN p_n;
        ELSE
          RETURN p_n * factorial(p_n - 1);
      END IF;
  END;
/

---------------
CREATE OR REPLACE FUNCTION bd_fac (fn NUMBER)
   RETURN NUMBER
IS
BEGIN
   IF fn = 1
   THEN
      RETURN fn;
   ELSE
      RETURN fn * bd_fac (fn - 1);
   END IF;
END;
/

SELECT bd_fac(4) FROM dual