Delete duplicates MySQL table, leaving one row for each duplicate group
DELETE `t1`
FROM `table` `t1`
INNER JOIN `table` `t2`
ON `t1`.`dup_col1` = `t2`.`dup_col1`
AND `t1`.`dup_col2` = `t2`.`dup_col2`
# AND...
WHERE `t1`.`primary_key` > `t2`.`primary_key`