不是很明白什么意思, 这样么?
````sql
select a.receive_id, a.send_id, a.is_read, a.ctime
from message a
join (select receive_id, send_id
from message
where (receive_id = userid or send_id = userid)
order by ctime desc
limit 1) b on b.receive_id = a.receive_id and b.send_id = a.send_id
order by ctime desc;
````