How can I determine if a string is numeric in SQL?

Question

In a SQL query on Oracle 10g, I need to determine whether a string is numeric or not. How can I do this?

Answer 1

I don't have access to a 10G instance for testing, but this works in 9i:

CREATE OR REPLACE FUNCTION is_numeric (p_val VARCHAR2)
   RETURN NUMBER
IS
v_val   NUMBER;
BEGIN
   BEGIN
      IF p_val IS NULL OR TRIM (p_val) = ''
      THEN
         RETURN 0;
      END IF;

      SELECT TO_NUMBER (p_val)
        INTO v_val
        FROM DUAL;

      RETURN 1;
   EXCEPTION
      WHEN OTHERS
      THEN
         RETURN 0;
   END;
END;


SELECT is_numeric ('333.5') is_numeric
  FROM DUAL;

I have assumed you want nulls/empties treated as FALSE.