Answers for "easiest way to duplicate rows in mysql"

mysql get latest duplicate rows

SELECT
   t1.primary_id,
   t1.duplicate_id,
   t1.data1,
   t1.data2
FROM
   table_name t1
LEFT JOIN table_name t2
	ON (t1.duplicate_id = t2.duplicate_id AND t1.primary_id < t2.primary_id) 
WHERE
	t2.primary_id IS NULL

mysql delete duplicate rows except one

DELETE FROM NAMES
 WHERE id NOT IN (SELECT * 
                    FROM (SELECT MIN(n.id)
                            FROM NAMES n
                        GROUP BY n.name) x)