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

If you want to select only the numeric characters from your string, try using this:

CREATE FUNCTION IsNumeric (val varchar(255)) RETURNS tinyint 
 RETURN val REGEXP '^(-|\\+){0,1}([0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+|[0-9]+)$';

CREATE FUNCTION NumericOnly (val VARCHAR(255)) 
 RETURNS VARCHAR(255)
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 IsNumeric(SUBSTRING(val,idx,1)) = 0 THEN
   SET val = REPLACE(val,SUBSTRING(val,idx,1),"");
   SET idx = LENGTH(val)+1;
  END IF;
  SET idx = idx - 1;
  END WHILE;
  RETURN val;
 END;

---

Use it by calling the NumericOnly function like this:

select NumericOnly('1&2') as result;

Returns: "12"

select NumericOnly('abc987') as result;

Returns: "987"

(BTW, I wrote a post about this here)