cjthompson

-- Assume `Table` has 4 columns: id, col1, col2, col3

CREATE TABLE `dups` (
  `id` int(10) unsigned DEFAULT NULL,
  `hash` varbinary(32) DEFAULT NULL,
  KEY `id` (`id`),
  KEY `hash` (`hash`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO dups SELECT MIN(id) AS id, MD5(CONCAT(col1, col2, col3)) AS hash FROM `Table` GROUP BY col1, col2, col3 HAVING COUNT(*) > 1;