Question

我想列出列表中用户的所有消息。我能够列出所有邮件但我想要一份不同的发件人列表。它类似于facebook消息视图

我有消息表的这种布局

CREATE TABLE [dbo].[messages](
    [id] [bigint] IDENTITY(1,1) NOT NULL,
    [reciever] [varchar](50) NULL,
    [sender] [varchar](50) NULL,
    [posted] [datetime] NULL,
    [message] [varchar](1000) NULL,
    [status] [varchar](1) NULL
)

接收者和发件人是此表的外键

CREATE TABLE [dbo].[accounts](
    [uname] [varchar](50) NOT NULL,
    [pword] [varchar](32) NULL,
    [fname] [varchar](50) NULL,
    [mname] [varchar](50) NULL,
    [lname] [varchar](50) NULL
)

我尝试过这个查询，但它不起作用

SELECT [status], posted, sender, (
    SELECT DISTINCT sender FROM [messages] b
    WHERE a.sender = b.sender
) AS sender FROM [messages] a

目标是列出所有邮件，但不同/唯一的发件人。

提前致谢

Answer 1

我终于明白了！大声笑我只是在WITH查询块

中添加条件

WITH latestMessages
AS
(
    SELECT  ID, receiver, sender, posted, message, status,
        ROW_NUMBER() OVER (Partition BY Sender
                                ORDER BY posted DESC) RN
    FROM    messages
    WHERE   receiver = 'admin'


)
SELECT  ID, receiver, sender, posted, message, status
FROM    latestMessages 
WHERE   RN = 1

这是一种非常简单快捷的方法，而不是执行两个单独的查询。

PS：如何将其标记为已解决？

Answer 2

;WITH latestMessages
AS
(
    SELECT  ID, receiver, sender, posted, message, status,
            ROW_NUMBER() OVER (Partition BY Sender
                                ORDER BY posted DESC) RN
    FROM    messages
)
SELECT  ID, receiver, sender, posted, message, status
FROM    latestMessages 
WHERE   RN = 1

Answer 3

我能够解决这个问题。我所做的是列出收件人的所有邮件

SELECT DISTINCT sender FROM messages WHERE receiver = 'someuser'

然后获取接收器的最近消息

SELECT TOP (1) message, posted FROM messages WHERE receiver = 'someuser' AND sender = 'anotheruser' ORDER BY posted DESC

我是通过使用我使用的编程语言的一些函数来实现的，这是.NET

MSSQL，列出所有邮件但不同的发件人

3 个答案: