Hamming Distance

BITWISE XOR - HAMMING DISTANCE between two long HEX values <br/> <br/> e.g. find similar images or anything else that has a hashvalue <br/> <br/> comparehash - returns similarity in percent
/* MYSQL Function */ DELIMITER $$ DROP FUNCTION IF EXISTS comparehash $$ CREATE FUNCTION comparehash (hash1 varchar(256), hash2 varchar(256), maxlen int) RETURNS float DETERMINISTIC BEGIN DECLARE hashpart1 varchar(64) DEFAULT ""; DECLARE hashpart2 varchar(64) DEFAULT ""; DECLARE bitcnt int DEFAULT 0; DECLARE strlen int DEFAULT 16; DECLARE i int DEFAULT 0; DECLARE len int DEFAULT 0; SET len = LENGTH(hash1) / strlen; WHILE i<len AND i < maxlen DO SET hashpart1 = SUBSTRING(hash1,(i*strlen)+1,strlen); SET hashpart2 = SUBSTRING(hash2,(i*strlen)+1,strlen); SET bitcnt = bitcnt + bit_count(cast(conv(hashpart1, 16, 10) as unsigned) ^ cast(conv(hashpart2, 16, 10) as unsigned)); SET i = i+1; END WHILE; RETURN ((64*i)-bitcnt)*100.0/(64*i); END $$ DELIMITER ;

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Language: SQL | User: J√∂rg | Created: Oct 21, 2013 | Tags: mysql hash hex compare hamming distance function