mysql - ORDER BY 在 GROUP BY 之前

Question

我有一个页面显示了与您聊天的人的列表。目前它显示的是您一直与之聊天的人，以及最旧的消息。但是，它应该显示 NEWEST 消息。这是查询:

SELECT * FROM post
WHERE fk_user_to = '$userid'
GROUP BY fk_user_from
ORDER BY datotime DESC

和表结构

post_id || fk_user_to || fk_user_from || message || datotime

Answer 1

结果是:

    SELECT * FROM
    (SELECT * FROM post ORDER BY datotime DESC) as inv
    WHERE fk_user_to = '$userid'
    GROUP BY fk_user_from
    ORDER BY datotime DESC