从 sql 获取当前用户和其他用户之间的最后一条消息

Question

我想检索当前用户和其他人之间的最后一条消息，并将其显示在用户的消息页面中，就像 facebook 一样。我用过这个

select *
from ch_messages
where receiver='$current_user_id' or sender='$current_user_id' && (least(sender, receiver), greatest(sender, receiver), f_msg_date)     
in 
(
    select 
       least(sender, receiver) as x, greatest(sender, receiver) as y, 
       max(f_msg_date) as date
    from ch_messages
    group by sender, receiver
)

但它会获取从用户到当前用户的所有消息以及当前用户给用户的最后一条消息。 I want it like this image

这是我的表结构

mid  => messages id
sender  => The sender of the message
receiver => The receiver of the message
msg   => The message sent
f_msg_date => date in which the message was sent

Answer 1

您只需要在子查询中删除 reciver 周围的引号，然后 如果您想要最后一条消息，假设每条消息都有一个唯一的 id 列（自动递增）

  select *
  from ch_messages
  where receiver='$current_user_id' 
  or sender='$current_user_id' 
  AND ( id, least(sender, receiver), greatest(sender, receiver), f_msg_date )     
  in 
  (  select 
           max(id) 
         , least(sender, receiver) 
         , greatest(sender, receiver), 
           max(f_msg_date) 
      from ch_messages
      group by sender, receiver
  )