How to only select numeric data from mysql?

Question

Does mysql have a function like is_num() which can allow me determine the data is numeric or not?

Answer 1

Thousand times faster.

DROP FUNCTION IF EXISTS NumericOnly;
DELIMITER $$
CREATE FUNCTION NumericOnly(val VARCHAR(25)) RETURNS VARCHAR(25)
BEGIN
 DECLARE idx INT DEFAULT 0;
  IF ISNULL(val) THEN RETURN NULL; END IF;
  IF LENGTH(val) = 0 THEN RETURN ""; END IF;

 SET idx = LENGTH(val);
  WHILE idx > 0 DO
  IF (SUBSTRING(val,idx,1) in ('0','1','2','3','4','5','6','7','8','9')) = 0 THEN
   SET val = CONCAT(SUBSTRING(val, 1, idx-1), SUBSTRING(val FROM idx + 1));
  END IF;
  SET idx = idx - 1;
  END WHILE;
  RETURN val;
END;
$$
DELIMITER ;