如何计算MYSQL中两个字符串之间的相似度

如果我在 mysql 中有两个字符串:

<前>@a="欢迎使用堆栈溢出"@b="你好堆栈溢出";

有没有办法使用 MYSQL 获得这两个字符串之间的相似度百分比?例如，这里有 3 个词是相似的，因此相似度应该是这样的:
count(@a 和@b 之间的相似词)/(count(@a)+count(@b) - count(intersection))
因此结果是 3/(4 + 4 - 3)= 0.6
任何想法都受到高度赞赏！

解决方案

你可以使用这个功能(cop^H^H^Hadapted from http://www.artfulsoftware.com/infotree/queries.php#552):

CREATE FUNCTION `levenshtein`( s1 text, s2 text) 返回 int(11)确定性开始声明 s1_len, s2_len, i, j, c, c_temp, cost INT;声明 s1_char CHAR;声明 cv0、cv1 文本；SET s1_len = CHAR_LENGTH(s1), s2_len = CHAR_LENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0;如果 s1 = s2 那么返回 0;ELSEIF s1_len = 0 那么返回 s2_len;ELSEIF s2_len = 0 那么返回 s1_len;别的当 j <= s2_len 时SET cv1 = CONCAT(cv1, UNHEX(HEX(j))), j = j + 1;结束时；当 i <= s1_len 时SET s1_char = SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1;当 j <= s2_len 时SET c = c + 1;如果 s1_char = SUBSTRING(s2, j, 1) THEN设置成本 = 0;ELSE SET 成本 = 1;万一;SET c_temp = CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + 成本；如果 c >c_temp THEN SET c = c_temp;万一;SET c_temp = CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1;如果 c >c_temp THENSET c = c_temp;万一;SET cv0 = CONCAT(cv0, UNHEX(HEX(c))), j = j + 1;结束时；设置 cv1 = cv0, i = i + 1;结束时；万一;返回 c;结尾

为了获得 XX% 使用这个函数

CREATE FUNCTION `levenshtein_ratio`( s1 text, s2 text ) 返回 int(11)确定性开始声明 s1_len、s2_len、max_len INT；设置 s1_len = LENGTH(s1), s2_len = LENGTH(s2);如果 s1_len >s2_len 那么设置 max_len = s1_len;别的设置 max_len = s2_len;万一;返回 ((1 - LEVENSHTEIN(s1, s2)/max_len) * 100);结尾

if i have two strings in mysql:

@a="Welcome to Stack Overflow"
@b=" Hello to stack overflow";

is there a way to get the similarity percentage between those two string using MYSQL? here for example 3 words are similar and thus the similarity should be something like:
count(similar words between @a and @b) / (count(@a)+count(@b) - count(intersection))
and thus the result is 3/(4 + 4 - 3)= 0.6
any idea is highly appreciated!

解决方案

you can use this function (cop^H^H^Hadapted from http://www.artfulsoftware.com/infotree/queries.php#552):

CREATE FUNCTION `levenshtein`( s1 text, s2 text) RETURNS int(11)
    DETERMINISTIC
BEGIN 
    DECLARE s1_len, s2_len, i, j, c, c_temp, cost INT; 
    DECLARE s1_char CHAR; 
    DECLARE cv0, cv1 text; 
    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

and for getting it as XX% use this function

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