mysql levenshtein函数

$word = mysql_real_escape_string($word);mysql_qery("SELECT `term` FROM `words` WHERE levenshtein('$word', `term`) BETWEEN 0 AND 4");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 ;