具有结果限制的SQL

我正在做一个简单的聊天，需要一种方法，只获得10条“消息”公关对话，但不知道如何做到这一点

这是我已经尝试过的。 我的SQL：

现在我得到了用户ID 1234的所有消息。。。但我只想要10条公共对话信息

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希望有意义

标准SQL方法是使用窗口/分析函数：

SELECT t.*
FROM (SELECT c.*, su.name as sender_name, ru.name as receiver_name,
             row_number() over (partition by c.conversation order by c.created desc) as seqnum
      FROM chat c INNER JOIN
           users su
           ON su.id = c.sender_user_id INNER JOIN
           users ru
           ON ru.id = c.receiver_user_id
      WHERE sender_user_id = '1234' OR receiver_user_id = '1234'
     ) t
WHERE seqnum <= 10
ORDER BY created ASC;

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您需要一种在标准SQL中工作的技术，还是忘记标记问题了？是的。例如，选择MSSQL的前10个*和MySQL的限制10。让我加入Oracle的乐趣：。。。。。。。如果rownum（）没有看到DDL，就有点难以确定地回答，特别是（我怀疑）您有两个名为

id

（chat.id和users.id）的列，我希望可以在MySQL中完成，我的错。非常感谢。。。但我得到了这个错误：语法使用near'（按c.conversation order按c.created desc划分）作为seqnum。。。知道吗？你在用哪个数据库？SQL server 2008不支持此语法。

SELECT t.*
FROM (SELECT c.*, su.name as sender_name, ru.name as receiver_name,
             row_number() over (partition by c.conversation order by c.created desc) as seqnum
      FROM chat c INNER JOIN
           users su
           ON su.id = c.sender_user_id INNER JOIN
           users ru
           ON ru.id = c.receiver_user_id
      WHERE sender_user_id = '1234' OR receiver_user_id = '1234'
     ) t
WHERE seqnum <= 10
ORDER BY created ASC;

SELECT t.*
FROM (SELECT c.*, su.name as sender_name, ru.name as receiver_name,
             (@rn := if(@c = c.conversation, @rn + 1,
                        if(@c := c.conversation, 1, 1)
                       )
             ) as seqnum
      FROM chat c INNER JOIN
           users su
           ON su.id = c.sender_user_id INNER JOIN
           users ru
           ON ru.id = c.receiver_user_id CROSS JOIN
           (SELECT @c := 0, @rn := 0) vars
      WHERE sender_user_id = '1234' OR receiver_user_id = '1234'
      ORDER BY c.conversation, c.created desc
     ) t
WHERE seqnum <= 10
ORDER BY created ASC;