SELECT * from(
SELECT * FROM(
SELECT
im.message_id,im.message_receiver as mobile,im.message_content
FROM
iddb.id_im_message as im
WHERE
im.message_sender = '13005066609' AND im.message_receiver<> '13005066609'
UNION
SELECT
im.message_id,im.message_sender as mobile,im.message_content
FROM
iddb.id_im_message as im
WHERE
im.message_receiver = '13005066609' AND im.message_sender<> '13005066609'
) as a ORDER BY a.message_id DESC) as b GROUP BY b.mobile ORDER BY b.message_id DESC ;