mysql 查相似度

CREATE TABLE articles (
    id INT AUTO_INCREMENT PRIMARY KEY,
    title TEXT,
    content TEXT
);

ALTER TABLE articles ADD FULLTEXT(title, content);

INSERT INTO articles (title, content) VALUES
('Introduction to MySQL', 'MySQL is a popular relational database management system.'),
('Advanced MySQL', 'Learn advanced techniques for MySQL optimization.'),
('Introduction to PostgreSQL', 'PostgreSQL is another powerful relational database.');

SELECT * FROM articles WHERE MATCH(title, content) AGAINST('MySQL');

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(1);
    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(c)), j = 1;
            WHILE j <= s2_len DO
                SET cost = IF(s1_char = SUBSTRING(s2, j, 1), 0, 1), c = c + cost;
                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 //

DELIMITER ;

SELECT title, LEVENSHTEIN('MySQL', title) AS distance FROM articles WHERE LEVENSHTEIN('MySQL', title) <= 2;