Distância de Levenshtein usando Mysql

Um ótimo pedaço de código de http://snippets.aktagon.com/snippets/610-levenshtein-distance-for-mysql .. Marque com +1 no site!

DELIMITER $$
CREATE FUNCTION levenshtein
( s1 VARCHAR(255), s2 VARCHAR(255) )
RETURNS INT

DETERMINISTIC

BEGIN
DECLARE s1_len
, s2_len, i, j, c, c_temp, cost INT;
DECLARE s1_char CHAR
;
-- max strlen=255
DECLARE cv0
, cv1 VARBINARY(256);
SET s1_len
= CHAR_LENGTH(s1), s2_len = CHAR_LENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0;
IF s1
= s2 THEN
RETURN
0;
ELSEIF s1_len
= 0 THEN
RETURN s2_len
;
ELSEIF s2_len
= 0 THEN
RETURN s1_len
;
ELSE

WHILE j
<= s2_len DO
SET cv1
= CONCAT(cv1, UNHEX(HEX(j))), j = j + 1;
END WHILE;
WHILE i
<= s1_len DO
SET s1_char
= SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1;
WHILE j
<= s2_len DO
SET c
= c + 1;
IF s1_char
= SUBSTRING(s2, j, 1) THEN
SET cost
= 0; ELSE SET cost = 1;
END IF;
SET c_temp
= CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + cost;
IF c
> c_temp THEN SET c = c_temp; END IF;
SET c_temp
= CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1;
IF c
> c_temp THEN
SET c
= c_temp;
END IF;
SET cv0
= CONCAT(cv0, UNHEX(HEX(c))), j = j + 1;
END WHILE;
SET cv1
= cv0, i = i + 1;
END WHILE;
END IF;
RETURN c
;
END$$


CREATE FUNCTION levenshtein_ratio
( s1 VARCHAR(255), s2 VARCHAR(255) )
RETURNS INT

DETERMINISTIC

BEGIN
DECLARE s1_len
, s2_len, max_len INT;
SET s1_len
= LENGTH(s1), s2_len = LENGTH(s2);
IF s1_len
> s2_len THEN
SET max_len
= s1_len;
ELSE

SET max_len
= s2_len;
END IF;
RETURN ROUND
((1 - LEVENSHTEIN(s1, s2) / max_len) * 100);
END$$

DELIMITER
;

#######

select levenshtein('butt', 'but') from test;
select levenshtein_ratio('butt', 'but') from test;