Question

我有一张桌子：

messages( id, owner, author, message, chat_id, message_date)

我希望获得最后留言信息的聊天列表。我怎么能这样做？

我试过

SELECT MAX(message_date), id, owner, author, message, chat_id 
FROM messages WHERE owner = ? GROUP BY chat_id

但它没有用。

Answer 1

您可以使用row_number获取最新消息以及相应的日期。

select message_date, id, owner, author, message, chat_id
from (
SELECT row_number() over(partition by chat_id order by message_date desc) as rn,
message_date, id, owner, author, message, chat_id 
FROM messages WHERE owner = ? ) t
where rn = 1

Answer 2

你想要每个chat_id，但只有最新的条目，如果有几条消息？

SELECT message_date, id, owner, author, message, chat_id
FROM messages m1
WHERE owner = ?
where not exists (select 1 from messages m2
                  where m2.chat_id = m1.chat_id
                    and m2.message_date > m1.message_date)

仅当相同的聊天没有后续条目时才返回一行。

如何从聊天中获取最后的消息？

2 个答案: