SQL:如何基于最大日期时间为多个ID选择单个记录? [英] SQL: how to select single record for multiple id's on the basis of max datetime?

问题描述

我有以下SQL表，

Id      WindSpeed      DateTime
--------------------------------------
1       1.1            2009-09-14 16:11:38.383
1       1.9            2009-09-15 16:11:38.383
1       2.0            2009-09-16 16:11:38.383
1       1.8            2009-09-17 16:11:38.383
1       1.7            2009-09-19 16:11:38.382
2       1.9            2009-09-19 16:11:38.383
1       1.6            2009-09-19 16:11:38.383
2       1.2            2009-09-20 16:11:38.383

我想编写一个查询，该查询将从上表中返回以下结果集:

I want to write a query which will return me the following result set from the above table:

Id      WindSpeed      DateTime
--------------------------------------
1       1.6            2009-09-19 16:11:38.383
2       1.2            2009-09-20 16:11:38.383

上面的重用包含最新的(基于该id的最新日期时间)单个条目.这意味着我的日期时间有多个记录ID.

The above reuslt contains the latest (on the basis of latest datetime for that id) single entry. Which means I have multiple record id's with datetime.

我想获取所有ID的最新单项.

I want to get the latest single entry of all id's.

推荐答案

SELECT        a.Id, a.WindSpeed, a.DateTime
FROM          YourTable AS a
INNER JOIN     
(
    SELECT    ID, Max(DateTime) AS DateTime
    FROM      YourTable
    GROUP BY  ID
) AS b
ON            a.ID = b.ID
AND           a.DateTime = b.DateTime

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