Implement ISNUMERIC function in SQL

a)
CREATE OR REPLACE FUNCTION isNumeric1 (p_num VARCHAR2)
 RETURN VARCHAR2
IS
 result VARCHAR2 (50);
BEGIN
 SELECT LENGTH (TRANSLATE (TRIM (p_num), ' +-.0123456789', ' ')) INTO result FROM DUAL;
 RETURN result;
END;
/
      It will return null if numeric, return count if non numeric characters otherwise.

b)
CREATE OR REPLACE FUNCTION isNumeric2 (p_num VARCHAR2)
 RETURN NUMBER
IS
 result NUMBER;
BEGIN
 SELECT INSTR (TRANSLATE (P_NUM, 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'), 'X') INTO result FROM DUAL;

 RETURN result;
END;
/

    It returns 0 if it is a number, 1 if it is non-numeric.