mysql - 使用线程和消息构建收件箱查询

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

我想构建一个查询来获取我的线程：

1. 该线程的最新消息
2. 该线程的 id

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

有什么想法吗？

更新：

表关系：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

在我的头顶上：

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);

[编辑] 经过测试，它似乎工作正常。

Answer 3

试试这个

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