消息功能创建 Sql 查询和数据库视图

Question

鉴于以下情况：

我需要能够获取给定用户参与的所有线程的列表，首先按最近的消息排序，仅显示最近的消息（每个线程 1 条消息）

这是上面的 SQL 查询：

SELECT
    Message.MessageId,
    Message.CreateDate,
    Message.Body,
    Login.Username,
    (SELECT MessageReadState.ReadDate
        FROM MessageReadState
        WHERE MessageReadState.MessageId = Message.MessageId
            AND MessageReadState.LoginId = 2) AS ReadState
FROM Message INNER JOIN Login ON Message.SenderLoginId = Login.LoginId
WHERE Message.MessageId IN (
    SELECT Max(Message.MessageId)
    FROM MessageThreadParticipant
    INNER JOIN Message
        ON MessageThreadParticipant.MessageThreadId = Message.MessageThreadId
    WHERE MessageThreadParticipant.LoginId=2
    GROUP BY MessageThreadParticipant.MessageThreadId
)
ORDER BY Message.CreateDate DESC;

它的工作方式是这样的。一个 LoginId 1 向一个 LoginId 2 发送一条消息：

1. 创建一个新线程并将一条记录插入到 MessageThread 中

2. 一条新记录被添加到消息表中，上面的treadId

3. MessageThreadParticipant 中插入了两条记录（Sender LoginId 和 Recipient LogiId）

   当用户打开他/她的消息列表时，MessageReadState 将更新消息的 ReadDate。

问题： 我想创建一个视图，我可以在其中简单地过滤 LoginId（我将使用 LINQ）。但是我不能用上面的查询来做到这一点（因为我需要在 sql 语句中的某处传递 loginId）。有没有办法以允许我查看的方式修改上述 SQL 查询？这是什么？

编辑： 我想我有，但我不确定这是否是最好/最有效的解决方案：

SELECT
    Message.MessageId,
    Message.MessageThreadId,
    Message.SenderLoginId,
    Mtp.LoginId,
    Login.Username,
    Message.CreateDate,
    Message.Body,
    (SELECT MessageReadState.ReadDate
        FROM MessageReadState
        WHERE MessageReadState.MessageId = Message.MessageId
            AND MessageReadState.LoginId = Mtp.LoginID) AS ReadState
FROM Message 
    INNER JOIN Login ON Message.SenderLoginId = Login.LoginId
    INNER JOIN MessageThreadParticipant Mtp ON Mtp.MessageThreadId = Message.MessageThreadId
WHERE Message.MessageId IN (
    SELECT Max(Message.MessageId)
    FROM MessageThreadParticipant
    INNER JOIN Message
        ON MessageThreadParticipant.MessageThreadId = Message.MessageThreadId
    WHERE MessageThreadParticipant.LoginId=Login.LoginID
    GROUP BY MessageThreadParticipant.MessageThreadId
)
ORDER BY Message.CreateDate DESC;

Answer 1

这是否符合您的要求？

SELECT
  Login.LoginID,
  Login.Username,
  Message.MessageThreadID,
  Message.MessageId,
  Message.CreateDate,
  Message.Body,
  Sender.LoginID                     AS SenderLoginID,
  Sender.Username                    AS SenderUsername,
  MessageReadState.ReadDate          AS RecipientReadDate
FROM
  Login
INNER JOIN
  MessageThreadParticipant
    ON MessageThreadParticipant.LoginId = Login.LoginID
-- This gives all threads every LoginID has ever participated in

CROSS APPLY
  (SELECT TOP 1 * FROM Message WHERE ThreadId = MessageThreadParticipant.MessageThreadId ORDER BY CreateDate DESC) AS Message
-- This gives the newest message for each of those threads.
-- The Login.LoginID could be either the Sender or Recipient

INNER JOIN
  Login AS [Sender]
    ON Sender.LoginID = Message.SenderLoginID
LEFT JOIN
  MessageReadState
    ON  MessageReadState.MessageID = Message.MessageID
    AND MessageReadState.LoginId <> Sender.LoginID
-- This gets the Sender's details, and tries to get whether the recipient read the message
-- It assumes the only MessageReadState entries are for the Sender and Recipient.

ORDER BY
  Message.CreateDate DESC;