DROP FUNCTION IF EXISTS `levenshtein`;
CREATE FUNCTION `levenshtein`(`s1` VARCHAR(255) CHARACTER SET utf8, `s2` VARCHAR(255) CHARACTER SET utf8)
    RETURNS TINYINT UNSIGNED
    NO SQL
    DETERMINISTIC
BEGIN
    DECLARE s1_len, s2_len, i, j, c, c_temp TINYINT UNSIGNED;
    -- max strlen=255 for this function
    DECLARE cv0, cv1 VARBINARY(256);
    
    -- if any param is NULL return NULL
    -- (consistent with builtin functions)
    IF (s1 + s2) IS NULL THEN
        RETURN NULL;
    END IF;
    
    SET s1_len = CHAR_LENGTH(s1),
        s2_len = CHAR_LENGTH(s2),
        cv1 = 0x00,
        j = 1,
        i = 1,
        c = 0;
    
    -- if any string is empty,
    -- distance is the length of the other one
    IF (s1 = s2) THEN
        RETURN 0;
    ELSEIF (s1_len = 0) THEN
        RETURN s2_len;
    ELSEIF (s2_len = 0) THEN
        RETURN s1_len;
    END IF;
    
    WHILE (j <= s2_len) DO
        SET cv1 = CONCAT(cv1, CHAR(j)),
        j = j + 1;
    END WHILE;
    
    WHILE (i <= s1_len) DO
        SET c = i,
            cv0 = CHAR(i),
            j = 1;
        
        WHILE (j <= c_temp) THEN
                SET c = c_temp;
            END IF;
            
            SET c_temp = ORD(SUBSTRING(cv1, j+1, 1)) + 1;
            IF (c > c_temp) THEN
                SET c = c_temp;
            END IF;
            
            SET cv0 = CONCAT(cv0, CHAR(c)),
                j = j + 1;
        END WHILE;
        
        SET cv1 = cv0,
            i = i + 1;
    END WHILE;
    
    RETURN c;
END;

    SELECT `preparat`.`prep` FROM `preparat` 
    INNER JOIN `preparat_myisam` 
    ON `preparat_myisam`.`id` = `preparat`.`id` 
    WHERE MATCH(`preparat_myisam`.prep) AGAINST ('пирин' IN BOOLEAN MODE) >0
    ORDER BY MATCH(`preparat_myisam`.prep) AGAINST ('пирин' IN BOOLEAN MODE) DESC