CREATE FUNCTION IS_NUMERIC (ARG VARCHAR(2000))
RETURNS CHAR(5)
LANGUAGE SQL
DETERMINISTIC
------------------------------------------------------------------
-- SQL function to return determine if a a string is numeric
------------------------------------------------------------------
RETURN
WITH NUMERIC_ARRAY (NUM) AS
(
VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)
)
, FIND_NUMERICS (ISNUM, NUM_TEST, COUNTER) AS
(

    SELECT 0
    ,      NUM
    ,      0
    FROM   NUMERIC_ARRAY

    UNION ALL

    SELECT LOCATE (CAST(NUM_TEST AS CHAR(1)),(SUBSTR(ARG,COUNTER+1,1)))
    ,      NUM_TEST
    ,      COUNTER + 1
    FROM   FIND_NUMERICS F
    WHERE  COUNTER < LENGTH(ARG)

)
-- An 'ISNUM' value of 1 should be present for every char if all numerics
VALUES (
        CASE WHEN LENGTH (ARG) > (SELECT COUNT(1) FROM FIND_NUMERICS WHERE ISNUM = 1)
         THEN 'FALSE'
         ELSE 'TRUE'
        END
       )
;