The Levenshtein distance between two words is the minimum number of single-character edits (insertion, deletion, substitution) required to change one word into the other. – Wikipedia
To implement in MySQL, use the following function – if using phpmyadmin you will need to set a different delimiter such as ‘$’ instead of ‘;’ to create this function.
CREATE FUNCTION levenshtein( s1 VARCHAR(255), s2 VARCHAR(255) ) RETURNS INT DETERMINISTIC BEGIN DECLARE s1len, s2len, i, j, c, ctemp, cost INT; DECLARE s1char CHAR; -- max strlen=255 DECLARE cv0, cv1 VARBINARY(256); SET s1len = CHARLENGTH(s1), s2len = CHARLENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0; IF s1 = s2 THEN RETURN 0; ELSEIF s1len = 0 THEN RETURN s2len; ELSEIF s2len = 0 THEN RETURN s1len; ELSE WHILE j <= s2len DO SET cv1 = CONCAT(cv1, UNHEX(HEX(j))), j = j + 1; END WHILE; WHILE i <= s1len DO SET s1char = SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1; WHILE j <= s2len DO SET c = c + 1; IF s1char = SUBSTRING(s2, j, 1) THEN SET cost = 0; ELSE SET cost = 1; END IF; SET ctemp = CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + cost; IF c > ctemp THEN SET c = ctemp; END IF; SET ctemp = CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1; IF c > ctemp 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;
The following is example usage – it returns the name column ordered by the Levenshtein distance – the lowest number is the closest match.
SELECT name, LEVENSHTEIN(name, 'string') AS distance FROM table ORDER BY distance ASC