Question

我有两个表，conversation_tbl和conversation_reply_tbl

conversation_reply_tbl
-------------------------
|  conversation_reply_id|   //auto increment id      
|  reply_message        |   //message text
|  user_id              |   //the user who sent the message
|  datetime_sent        |   //date and time of message sent
|  status               |   //values '0' or '1' (read or not)
|  conversation_id      |   //relation to the conversation
-------------------------

conversation_tbl
-------------------------
|  conversation_id      |    //auto increment id     
|  from_user            |    //the user who sent the message
|  to_user              |    //the recipient
|  datetime_created     |    //date of the message created
|  gallery_id           |//the gallery where the message started from
-------------------------

现在，我使用conversation_reply_tbl存储会话中发生的所有消息，并使用conversation_tbl存储会话主数据。

现在，我想选择用户参与的所有会话，但我想显示每个会话的最新消息，就像在着名网站和应用程序（例如'WhatsApp'或'Facebook'）中所做的一样。

这可以在一个查询中完成，还是必须使用PHP函数？

Answer 1

以下是使用一个查询获取该信息的方法：

select     t.*,
           last.*
from       conversation_tbl t
inner join (select   conversation_id, max(conversation_reply_id) conversation_reply_id
            from     conversation_reply_tbl
            group by conversation_id) all_lasts
        on all_lasts.conversation_id = t.conversation_id
inner join conversation_reply_tbl last
        on last.conversation_reply_id = all_lasts.conversation_reply_id
left join  (select   conversation_id 
            from     conversation_reply_tbl
            where    user_id = :the_user_id
            group by conversation_id) user_conv
        on user_conv.conversation_id = t.conversation_id
where      (     user_conv.conversation_id is not null
           or    t.to_user = :the_user_id )

请注意left join，因为目标用户可能尚未回复消息，而是启动消息的 to_user 。 where子句使两种情况都成为or：如果消息线程有用户的消息，或者用户是发起消息的目标，则查询应返回该对话。

Answer 2

如果我理解您正在尝试正确执行的操作，那么这样的内容会在提供适当的conversation_id时为您提供记录。

获取用户所属的对话

SELECT conversation_id FROM conversation_tbl WHERE from_user = ?

使用该ID，获取最后发送的消息。

SELECT datetime_sent, reply_message FROM conversation_reply_tbl
WHERE datetime_sent IN (SELECT MAX(datetime_sent)
FROM conversation_reply_tbl WHERE conversation_id = ? )

Answer 3

我假设您将所有会话消息保存在conversation_reply_tbl表的reply_message列下。

在这种情况下，你可以尝试这个

SELECT T2.conversation_id, T2.reply_message
FROM conversation_tbl T1  INNER JOIN  conversation_reply_tbl T2 ON 
T1.conversation_id = T2.conversation_id
WHERE (T1.from_user = $userID OR T1.to_user = $userID)
GROUP BY T1.conversation_id
ORDER BY T2.datime_sent DESC;

从对话中选择最新消息

3 个答案: