mysql - SQL 对话/类似聊天​​的输出

Question

我正在尝试对 MySQL 表 I 进行类似对话的输出，如下所示:

Content           From           To           Date
Lorem             36             3            10-10-2014
Ipsum             3              36           10-12-2014
Dolor             36             4            11-10-2014

我希望它像对话一样输出，因此只会显示两个用户之间的最后一条消息(按日期排序)。因此 ID 为 36 的用户将看到上表，如下所示:

Content          From            To           Date           
Ipsum            3               36           10-12-2014
Dolor            36              4            11-10-2014

因此“Lorem”不会显示，因为 Ipsum 是同一用户之间的较新消息。

编辑:

我现在使用此查询，但如果这是由用户自己发送的，则不会输出最新消息:

SELECT content, sent
FROM personal_messages pm
INNER JOIN (
    SELECT MAX( id ) id, from_user, to_user
    FROM personal_messages
    WHERE from_user = 46 OR to_user = 46
    GROUP BY to_user, from_user
) pm2 ON pm.id = pm2.id
INNER JOIN users u ON pm.from_user = u.id
ORDER BY pm.sent

希望有人能帮助我，先谢谢了!

Answer 1

知道回答可能已经太晚了，但以防万一这对某些人有帮助1 - 下面的查询正是 OP 所要求的 - 4 个选择和 2 个连接。

$sql="
SELECT T2.maxDate, T2.user2_id, T2.ava, T2.userName,chat.user_to,chat.user_from,chat.body,chat.viewed FROM 
(SELECT T1.user2_id, users.userName, users.ava, max(cdate) maxDate FROM
            (SELECT chat.user_to user2_id, max(msg_time) cdate
                FROM chat WHERE chat.user_from=18
                GROUP BY chat.user_to
            union distinct
            (SELECT chat.user_from user2_id, max(msg_time) cdate
                FROM chat WHERE chat.user_to=18
                GROUP BY chat.user_from)) T1
            inner join users on (users.userID = T1.user2_id)
            group by T1.user2_id
            order by maxDate desc) T2
            join chat on (T2.maxDate = chat.msg_time) ORDER BY T2.maxDate DESC";