//公司需要我做一个根据每天用户注册数量生成一个折现图，sql如下，
//亲测好用，只是如果某一天没有注册的话，就不会显示日期

　　SELECT DATE_FORMAT(f.registDate, '%Y-%m-%d') AS dayRegist,COUNT(f.flowingId) AS dayRegister
　　FROM shop_invitation_flowerwater AS f
　　GROUP BY dayRegist

//以 2018-01-22 1:56:55为例

convert(nvarchar(22),CreateDate,10) 　　　　　　=> 2018-01-22

DATEPART(month,CreateDate)                    => 01

DATEPART(year,CreateDate)                     => 2018

//年

select datepart(YEAR,'2018-01-22')

select datepart(yyyy,'2018-01-22')

select datepart(yy,'2018-01-22')

//月

select datepart(MONTH,'2018-01-22')

select datepart(mm,'2018-01-22')

select datepart(m,'2018-01-22')

//日

select datepart(dd,'2018-01-22')

//季度

select datepart(qq,'2018-01-22')

//星期

select datepart(dw,'2018-01-22')

//一年中的第多少天

select datepart(dy,'2018-01-22')

//一年中的第多少周

select datepart(wk,'2018-01-22')

SELECT CONVERT(VARCHAR(22),GETDATE(),10)     --2018-01-22

SELECT CONVERT(VARCHAR(22),GETDATE(),221) 　 --01/22/2018

//按日分组： 2018-01-22

select convert(nvarchar(22),CreateDate,10) as Times,ISNULL(sum(Unit),0.0) as Drinking from pdt_Out

group by convert(nvarchar(22),CreateDate,10) 

//按月分组： 2018-01

select DATEPART(month,CreateDate) as Times,sum(Unit) as Totals from pdt_Out

group by DATEPART(month,CreateDate)

//按年分组： 2018

select DATEPART(year,CreateDate) as Times,sum(Unit) as Totals from pdt_Out

group by DATEPART(year,CreateDate)