当分区是DateTime列时，如何检索每个组的最大行数

Question

从MS SQL 2014开始，当分区是DateTime列时，我试图获得“In_Max”的最大值。

在我的示例中，我想要检索此行：

2017-12-17T02: 08: 46.4 | 19977300

SQL：

 SELECT DateTime,
        sum(In_Max) OVER (PARTITION BY CAST(DateTime as date)
                          ORDER BY DateTime ASC
                          ROWS BETWEEN 3 PRECEDING AND 3 FOLLOWING
                         ) AS sum1
 FROM  yourtable

http://sqlfiddle.com/#!6/91f0d/5

我是否必须从DateTime中提取日期和时间，然后应用排名？

Answer 1

如果你只想要一行，你可以使用TOP (1)和ORDER BY：

SELECT top (1) DateTime,
       sum(cast(In_Max as int)) OVER (PARTITION BY CAST(DateTime as date) ORDER BY DateTime ASC ROWS BETWEEN 3 PRECEDING AND 3 FOLLOWING) AS sum1
FROM  yourtable
ORDER BY sum1 DESC;

Here是SQL小提琴。

Answer 2

从你的评论到戈登的回答我收集你想要在给定月份每天获得最大的in_max。这仅仅是聚合：

select
  cast(datetime as date) as day,
  max(in_max) -- or sum if you want the sum and not the maximum
from yourtable
where year(datetime) = 2017 and month(datetime) = 12
group by cast(datetime as date);