字符串相似度处理函数

database

oracle里面查比如存储过程里面与表SALES有关jobs:

SELECT * FROM (SELECT a.name,upper(b.what)AS what,SYS.UTL_MATCH.edit_distance_similarity

(a.name,upper(b.what)) AS similarity FROM dba_source a,dba_jobs b

WHERE SYS.UTL_MATCH.edit_distance_similarity(a.name,upper(b.what))>80

AND upper(a.text) LIKE "%SALES%"

AND b.what NOT LIKE "%dbms_refresh%")

ORDER BY 3 DESC;

有自带相似度函数 SYS.UTL_MATCH.edit_distance_similarity 可以直接用。

mysql8里面我只查到了一个搜索相关的文档文档地址并不适合我自己用,找了一下大佬的文章,发现了一个能用的自定义函数,用于计算字符串相似度。

DELIMITER $$

CREATE DEFINER=`root`@`localhost` FUNCTION `COMPARE_STRING`( 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$$

DELIMITER ;

DELIMITER $$

CREATE DEFINER=`root`@`localhost` FUNCTION `SIMILARITY_STRING`(a text, b text) RETURNS double

BEGIN

RETURN ABS(((COMPARE_STRING(a, b) / length(b)) * 100) - 100);

END$$

DELIMITER ;

试了一下还挺好用的,一些逻辑可以自己再适当的修改。

而在gp里面,我找了许久,发现一个 fuzzystrmatch  看起来比较高档的函数,这个函数需要安装:

[gpadmin@SZWPLDB1085 ~]$ psql -d postgres -f $GPHOME/share/postgresql/contrib/fuzzystrmatch.sql

SET

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

CREATE FUNCTION

然后会在 postgres 库多出一些函数:

用法在文档地址

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