SQL：如何在选择多个记录时仅选择最新记录

因此，我想将这个“返回”的结果集转换为它下面的结果集，创建日期是最年轻（最新）的，表示最近添加的内容

PhoneNum    sourcetable      FullName         reference        Task                                         CreatedDate
    0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  16/03/2015 15:01:05
    0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  12/03/2015 16:58:22
    0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  12/03/2015 16:58:25
    0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  10/03/2015 12:29:50
    0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  12/03/2015 14:18:47
    0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  10/03/2015 12:40:21
    1   This is not important   Mr wilson smith 39158   This is different every time, but has been renamed  10/03/2015 12:07:14
    1   This is not important   Mr wilson smith 39158   This is different every time, but has been renamed  10/03/2015 12:07:14
    1   This is not important   Mr wilson smith 39158   This is different every time, but has been renamed  10/03/2015 12:07:13

我需要返回的内容：

PhoneNum    sourcetable     FullName       reference      Task                                           CreatedDate
0   This is not important   Mr john smith   39161   This is different every time, but has been renamed  12/03/2015 16:58:25
1   This is not important   Mr wilson smith 39158   This is different every time, but has been renamed  10/03/2015 12:07:14

到目前为止我所拥有的

select distinct d.PhoneNum,d.sourcetable,N.FullName,C.fk_applicationid as ref,t.Subject,t.CreatedDate 
from Dial d
join Database.dbo.DM_PhoneNumbers p on p.PhoneNum1 = d.PhoneNum collate latin1_general_CI_AS
join Database.dbo.DM_PhoneNumbers on p.PhoneNum2 = d.PhoneNum collate latin1_general_CI_AS
join Database.dbo.DM_ClientApplicants C on C.FK_ClientID = P.FK_ApplicationID
join Database.dbo.DM_Names N on c.FK_ClientID = N.FK_ApplicationID
join Database.dbo.Tasks T on T.FK_ApplicationID = c.FK_ApplicationID
where c.FK_ClientID in (39157,39160)

如有任何帮助，将不胜感激。

在末尾添加“order by”以获取订单，并首先添加“desc”

ORDER BY t.CreatedDate DESC

将GROUPBY添加到末尾

在select之后添加“top”，以限制返回的记录数

SELECT TOP 1 ...

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好的，再试一次

SELECT 
    person.PhoneNum,
    person.sourcetable,
    person.FullName,
    person.ref,

    t.Subject,t.CreatedDate 

FROM Database.dbo.Tasks t
JOIN (
    SELECT d.PhoneNum,d.sourcetable,N.FullName,C.fk_applicationid as ref
    FROM Dial d
    JOIN Database.dbo.DM_PhoneNumbers p on p.PhoneNum1 = d.PhoneNum collate latin1_general_CI_AS
    JOIN Database.dbo.DM_PhoneNumbers on p.PhoneNum2 = d.PhoneNum collate latin1_general_CI_AS
    JOIN Database.dbo.DM_ClientApplicants C on C.FK_ClientID = P.FK_ApplicationID
    JOIN Database.dbo.DM_Names N on c.FK_ClientID = N.FK_ApplicationID

    WHERE c.FK_ClientID in (39157,39160)

) person ON T.FK_ApplicationID = person.ref

ORDER BY t.CreatedDate DESC

在这里，我通过“最新优先”选择任务，并加入到每个人都有一个任务的子选定人员中

---

我没有你的db，希望它能工作或给你正确的方向。

你可以使用

ROW\u NUMBER（）

：

---

显然，您只需更改select语句即可获得所需的列。

您只需更改我添加的最后一行即可。仅选择每个客户端的最新日期：

select distinct d.PhoneNum,d.sourcetable,N.FullName,C.fk_applicationid as ref,t.Subject,t.CreatedDate 
from Dial d
join Database.dbo.DM_PhoneNumbers p on p.PhoneNum1 = d.PhoneNum collate latin1_general_CI_AS
join Database.dbo.DM_PhoneNumbers on p.PhoneNum2 = d.PhoneNum collate latin1_general_CI_AS
join Database.dbo.DM_ClientApplicants C on C.FK_ClientID = P.FK_ApplicationID
join Database.dbo.DM_Names N on c.FK_ClientID = N.FK_ApplicationID
join Database.dbo.Tasks T on T.FK_ApplicationID = c.FK_ApplicationID
where c.FK_ClientID in (39157,39160)
AND CreatedDate >= ALL (SELECT DISTINCT MAX(CreatedDate) FROM Tasks WHERE PhoneNum = d.PhoneNum)

---

这样，您将获得所有客户机，但每个客户机只获得最后添加的一行。

请使用rank函数查找旧记录，这是未经测试的！！希望这有帮助

SELECT * FROM (

    select distinct d.PhoneNum,d.sourcetable,N.FullName,C.fk_applicationid as ref,t.Subject,t.CreatedDate 
    , RANK() OVER ( PARTITION BY  N.FullName ORDER BY t.CreatedDate DESC ) AS iRank


    from Dial d
    join Database.dbo.DM_PhoneNumbers p on p.PhoneNum1 = d.PhoneNum collate latin1_general_CI_AS
    join Database.dbo.DM_PhoneNumbers on p.PhoneNum2 = d.PhoneNum collate latin1_general_CI_AS
    join Database.dbo.DM_ClientApplicants C on C.FK_ClientID = P.FK_ApplicationID
    join Database.dbo.DM_Names N on c.FK_ClientID = N.FK_ApplicationID
    join Database.dbo.Tasks T on T.FK_ApplicationID = c.FK_ApplicationID
    where c.FK_ClientID in (39157,39160)

) AS t 
WHERE t.iRank = 1

---

您应该在以下列中使用

groupby

：PhoneNum、FullName、Reference。以及CreatedDate列上的

max

函数。然后，

内部连接

，将结果连接到您现在的查询。仅供初学者参考。t.CreatedDate desc的订单应该是这样的。您是如何获得phnum 0的日期为

12/03/2015 16:58:25

的记录的？您的预期输出与您的要求不符NVM在我的其他评论中，我已删除。我忘了正确滚动。你的问题和标题之间也有点不协调。在标题中，你想要最古老的唱片，但在你的问题中，你想要最新的……如果我试图为约翰·史密斯先生和威尔逊先生牵线搭桥，这行得通吗？或者它只会吸引wilson先生/smith先生？将前1名改为前2名以获得2张记录，但只取决于他们的创建日期我刚刚尝试了这个，因为我担心它不会吸引两个人。啊，你想把他们分组这对他想做的事情不起作用。他不想要createdate订购的最新单记录，他想要的是每个电话号码的最新创建记录。这是正确的方法，但需要稍微修改以适合他的表/列/联接/等。考虑到你有4张向上投票，这个答案似乎对其他人有效，但对我有效，答案高于你的答案，谢谢你的帮助。答案基本相同，但他做了你的工作：）。很乐意帮忙。这是一个总体上更好的答案。

SELECT * FROM (

    select distinct d.PhoneNum,d.sourcetable,N.FullName,C.fk_applicationid as ref,t.Subject,t.CreatedDate 
    , RANK() OVER ( PARTITION BY  N.FullName ORDER BY t.CreatedDate DESC ) AS iRank


    from Dial d
    join Database.dbo.DM_PhoneNumbers p on p.PhoneNum1 = d.PhoneNum collate latin1_general_CI_AS
    join Database.dbo.DM_PhoneNumbers on p.PhoneNum2 = d.PhoneNum collate latin1_general_CI_AS
    join Database.dbo.DM_ClientApplicants C on C.FK_ClientID = P.FK_ApplicationID
    join Database.dbo.DM_Names N on c.FK_ClientID = N.FK_ApplicationID
    join Database.dbo.Tasks T on T.FK_ApplicationID = c.FK_ApplicationID
    where c.FK_ClientID in (39157,39160)

) AS t 
WHERE t.iRank = 1