Question

所以我有两个表来处理消息threads和messages。

messages:
id | thread | user_from | user_to | text | created

threads:
id | user_from | user_to | created | status

我想构建一个查询，用以获取线程：

该主题的最新消息
该线程的ID

到目前为止，我一直在处理这个问题，首先获取所有线程（当然有适当的限制），然后分别获取每个线程的最新消息。

有什么想法吗？

更新：

表格关系：messages。thread = threads。id

Answer 1

select t.id, max(m.id) as last_message_id
from threads t
left outer join messages m on m.thread = t.id
group by t.id

Answer 2

脱离我的头顶：

SELECT t.id, m.* FROM threads t
INNER JOIN messages m ON m.thread = t.id
WHERE m.id = 
   (SELECT id FROM messages WHERE thread = t.id ORDER BY id DESC LIMIT 1);

[edit]经过测试，似乎工作正常。

Answer 3

尝试这个

SELECT  a.id     AS ThreadID, 
        c.`text` AS LatestMessage
FROM    threads a 
            INNER JOIN
            (
                SELECT  thread, max(created) maxCreated
                FROM    messages
                GROUP BY thread
            ) b on a.id = b.thread 
            INNER JOIN messages c
                    on a.id = c.thread AND
                       b.maxCreated = c.created

使用线程和消息构建收件箱查询

3 个答案: