mysql正则替换函数

CREATE FUNCTION `regex_replace`(pattern VARCHAR(1000),replacement VARCHAR(1000),original text)
 RETURNS text CHARSET utf8
  DETERMINISTIC
BEGIN
  DECLARE temp text;
    DECLARE temp2 text;
  DECLARE ch VARCHAR(1);
  DECLARE i INT;
    DECLARE j INT;
  SET i = 1;
  SET temp = '';
    set temp2 ='';
    set j=1;
  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);
            SET temp = CONCAT(temp,ch);
      IF  temp REGEXP pattern THEN
                set j=i;
                set temp2 ='';
                loop_label2: LOOP
                     IF j<1 THEN
                        LEAVE loop_label2;
                    END IF;
                    set temp2=CONCAT(SUBSTRING(temp,j-1,1),temp2);
                    IF  temp2 REGEXP pattern THEN
                        set temp = REPLACE(temp,temp2,replacement);
                        set temp2 ='';
                    end if;
                    set j=j-1;
                END LOOP;
                
      END IF;
      SET i=i+1;
    END LOOP;
  ELSE
    SET temp = original;
  END IF;
  RETURN temp;
END