MySQL正则替换函数

DELIMITER $$
CREATE FUNCTION  `regex_replace`(pattern VARCHAR(1000),replacement VARCHAR(1000),original VARCHAR(1000))
  RETURNS VARCHAR(1000)
  DETERMINISTIC
BEGIN
  DECLARE temp VARCHAR(1000);
  DECLARE ch VARCHAR(1);
  DECLARE i INT;
  SET i = 1;
  SET temp = '';
  IF original REGEXP pattern THEN
    loop_label: LOOP
      IF i>CHAR_LENGTH(original) THEN
        LEAVE loop_label;
      END IF;
      SET ch = SUBSTRING(original,i,1);
      IF NOT ch REGEXP pattern THEN
        SET temp = CONCAT(temp,ch);
      ELSE
        SET temp = CONCAT(temp,replacement);
      END IF;
      SET i=i+1;
    END LOOP;
  ELSE
    SET temp = original;
  END IF;
  RETURN temp;
END$$
DELIMITER ;