SQL：如何根據最大日期時間爲多個ID選擇單個記錄？

Question

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 

我想編寫一個查詢將返回我下面的結果從上面的表中設置：

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

以上reuslt包含了最新的（上該id的最新日期時間的基礎）單個條目。這意味着我有多個記錄ID與日期時間。

我想獲得所有id的最新單個條目。

Answer 1

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 

Answer 2

SELECT t1.Id, t1.WindSpeed, t1.DateTime 
    FROM table1 As t1 
WHERE t1.DateTime = (SELECT Max(DateTime) 
         FROM table1 As t2 
         WHERE t2.ID = t1.ID) 

Answer 3

這也應該做你想要什麼：

SELECT ID, WindSpeed, [DateTime] 
FROM (
    SELECT ROW_NUMBER() OVER (PARTITION BY ID ORDER BY [DateTime] DESC) AS RowNumber, 
     Id, WindSpeed, [DateTime] 
    FROM MyTable 
) T 
WHERE RowNumber = 1