CREATE OR REPLACE FUNCTION is_numeric (string IN VARCHAR2) RETURN BOOLEAN
/*
|| Function tests for NUMERIC characters, if 0-9 does NOT appear in the string then
||      FALSE is returned.
*/
IS
   i     NUMBER;
 v_boolean  BOOLEAN DEFAULT FALSE;
BEGIN
 FOR i in 1 .. length(string)
 LOOP
  IF substr(string,i,1) not between chr(48) and chr(57) THEN
      v_boolean := FALSE;
   EXIT;
  ELSE
   v_boolean := TRUE;
  END IF;
 END LOOP;
 RETURN(v_boolean);
END;
/