How to add levenshtein function in mysql?

Question

I got the code for Levenshtein distance for MySQL from http://kristiannissen.wordpress.com/2010/07/08/mysql-levenshtein/^{(archive.org link)}, but how to add that function in MySQL? I am using XAMPP and I need it for search in PHP.

Answer 1

I have connected to my MySQL server and simply executed this statement in MySQL Workbench, and it simply worked - I now have new function levenshtein().

For example, this works as expected:

SELECT levenshtein('abcde', 'abced')  2 

Answer 2

DELIMITER $$ CREATE FUNCTION levenshtein( s1 VARCHAR(255), s2 VARCHAR(255) )  RETURNS INT  DETERMINISTIC  BEGIN  DECLARE s1_len, s2_len, i, j, c, c_temp, cost INT;  DECLARE s1_char CHAR;  -- max strlen=255  DECLARE cv0, cv1 VARBINARY(256);  SET s1_len = CHAR_LENGTH(s1), s2_len = CHAR_LENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0;  IF s1 = s2 THEN    RETURN 0;  ELSEIF s1_len = 0 THEN    RETURN s2_len;  ELSEIF s2_len = 0 THEN    RETURN s1_len;  ELSE    WHILE j <= s2_len DO      SET cv1 = CONCAT(cv1, UNHEX(HEX(j))), j = j + 1;    END WHILE;    WHILE i <= s1_len DO      SET s1_char = SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1;      WHILE j <= s2_len DO        SET c = c + 1;        IF s1_char = SUBSTRING(s2, j, 1) THEN           SET cost = 0; ELSE SET cost = 1;        END IF;        SET c_temp = CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + cost;        IF c > c_temp THEN SET c = c_temp; END IF;          SET c_temp = CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1;          IF c > c_temp THEN             SET c = c_temp;           END IF;          SET cv0 = CONCAT(cv0, UNHEX(HEX(c))), j = j + 1;      END WHILE;      SET cv1 = cv0, i = i + 1;    END WHILE;  END IF;  RETURN c;  END$$ DELIMITER ;