Levenshtein MySQL-functions

levenshtein-ratio.sql

CREATE FUNCTION `LEVENSHTEIN_RATIO`( s1 text, s2 text ) RETURNS int(11)
    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

levenshtein.sql

CREATE FUNCTION `LEVENSHTEIN`( s1 VARCHAR(255), s2 VARCHAR(255) ) RETURNS int(11)
    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