获取最近联系人列表,显示联系人最新的一条消息

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 ;