分组和汇总列

Question

根据下表，（在两种服务器风格中）最佳方法是什么：

在分钟/小时/天之内将所有行分组，并获得最大的列“ CounterC”？

示例：在“现在”和“现在”之间-1天之间，每小时可获得Max（CounterC）。 示例2：在“现在”和“现在”之间-30天，每天获取Max（CounterC）。

显然，行必须分组，但是如何？

MS SQL

CREATE TABLE [dbo].[DE0000000D102D1D](
[index] [bigint] IDENTITY(1,1) NOT NULL,
[TimeStamp] [datetime] NOT NULL,
[CounterA] [bigint] NOT NULL,
[CounterB] [bigint] NOT NULL,
[CounterC] [bigint] NOT NULL,
[CounterD] [bigint] NOT NULL,
)

的MySQL

CREATE TABLE `de0000000d102d1d` (
 `index` bigint(20) NOT NULL AUTO_INCREMENT,
 `TimeStamp` datetime NOT NULL,
 `CounterA` bigint(20) NOT NULL,
 `CounterB` bigint(20) NOT NULL,
 `CounterC` bigint(20) NOT NULL,
 `CounterD` bigint(20) NOT NULL,
 PRIMARY KEY (`index`)
)

一些示例数据：

index  TimeStamp                CounterA  CounterB  CounterC   CounterD
-----  -----------------------  --------  --------  ---------  --------
1      2011-03-07 14:25:32.000  0         1         347406352  916
2      2011-03-07 14:26:32.000  0         1         347407169  916
3      2011-03-07 14:27:32.000  0         1         347407978  916
4      2011-03-07 14:28:31.000  0         1         347408617  916
5      2011-03-07 14:29:31.000  0         1         347409087  916
6      2011-03-07 14:30:30.000  0         1         347409557  916
7      2011-03-07 14:31:09.000  0         1         347409845  916

提前致谢！

编辑：实际上是每个间隔我想要的Max（CounterC），而不是总和。

Answer 1

对于SQL Server

-- Last 30 days grouped by day
select dateadd(day, datediff(day, 0, D.[TimeStamp]), 0) as [day], 
       max(D.CounterC) as MaxC
from DE0000000D102D1D as D
where D.[TimeStamp] between dateadd(d, -30, getdate()) and getdate()
group by dateadd(day, datediff(day, 0, D.[TimeStamp]), 0)

-- Last day grouped by the hour
select dateadd(hour, datediff(hour, 0, D.[TimeStamp]), 0) as [Hour], 
       max(D.CounterC) as MaxC
from DE0000000D102D1D as D
where D.[TimeStamp] between dateadd(d, -1, getdate()) and getdate()
group by dateadd(hour, datediff(hour, 0, D.[TimeStamp]), 0)

Answer 2

对于MySQL，这是相同的查询：

-- Last 30 days grouped by day
select date_format( timestamp,'%Y:%m:%d' ) `day`, max(D.CounterC) as MaxC
from `DE0000000D102D1D` as D
where D.`TimeStamp` between timestampadd(day, -30, now()) and now()
group by date_format( timestamp,'%Y:%m:%d' )
order by `day` ASC;

-- Last day grouped by the hour
select date_format( timestamp,'%Y:%m:%d %H' ) as `Hour`, max(D.CounterC) as MaxC
from `DE0000000D102D1D` as D
where D.`TimeStamp` between timestampadd(day, -1, now()) and now()
group by date_format( timestamp,'%Y:%m:%d %H' )
order by `Hour` ASC;