Sql 如何请求在房间中显示最新消息

我在聊天。我有4张桌子：

房间

信息

客人

使用者

在messages表中存储消息，在Users-Users表中，Guest-将访客存储在房间中。房间就像一个对话或对话。 我想请求获取特定用户为客人的每个房间的最新消息

SELECT DISTINCT TOP (15) r.id_room, r.type_room, r.name_room,
    m.content_message, m.image_message,
    m.file_message, m.date_message, u.person
    FROM Rooms AS r
      INNER JOIN Guest AS g ON g.id_room = r.id_room
      INNER JOIN Users AS u ON u.id_user = g.id_user
      INNER JOIN Messages AS m ON m.id_room = r.id_room
        WHERE g.id_user = 'OCI59TNG8ZZ'
        ORDER BY m.date_message DESC

他显示了房间里的所有信息

我认为如果没有重复的id_房间，这个请求会很好。 但是我不知道怎么做你可以试试这个：

SELECT  id_room,
        type_room,
        name_room,
        content_message,
        image_message,
        file_message,
        date_message,
        person
FROM    (
            SELECT  r.id_room,
                    r.type_room,
                    r.name_room,
                    m.content_message,
                    m.image_message,
                    m.file_message,
                    m.date_message,
                    u.person,
                    ROW_NUMBER() OVER(PARTITION BY R.ID_ROOM ORDER BY m.date_message DESC)  AS  RN
            FROM    Rooms AS r
            INNER JOIN Guest AS g ON g.id_room = r.id_room
            INNER JOIN Users AS u ON u.id_user = g.id_user
            INNER JOIN Messages AS m ON m.id_room = r.id_room
            WHERE   g.id_user = 'OCI59TNG8ZZ'
        ) V1
WHERE   V1.RN = 1

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使用通用表表达式，如下所示：

WITH CTE AS (
            SELECT  r.id_room,
                    r.type_room,
                    r.name_room,
                    m.content_message,
                    m.image_message,
                    m.file_message,
                    m.date_message,
                    u.person,
                    ROW_NUMBER() OVER(PARTITION BY R.ID_ROOM ORDER BY m.date_message DESC)  rn
            FROM  Rooms AS r
            INNER JOIN Guest AS g ON g.id_room = r.id_room
            INNER JOIN Users AS u ON u.id_user = g.id_user
            INNER JOIN Messages AS m ON m.id_room = r.id_room
            WHERE   g.id_user Like 'OCI59TNG8ZZ'
        )

SELECT * FROM CTE WHERE rn = 1

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最好显示表格的DDL而不是图片。这是否回答了您的问题？您是否忘记了“结束”条款中的“DESC”？出于某种原因，m.date_的订单消息在该答案中不起作用…@Сцццц刚刚在“结束”条款中添加了DESC。它应该是有效的