查询：将数据库-表中-若干日期-按一天24小时，将所有日期同一时间的数据求和。
学习点：将数据按小时分组求和
1 declare @BgainTime varchar(50)=‘2017-11-01‘ 2 declare @EndTime varchar(50) =‘2017-12-01‘ 3 --每小时发药处方量 4 select ‘时间‘=datepart(hh,ReceiveTime),‘发药量‘=count(*) from Prescription 5 where ReceiveTime between @BgainTime and @EndTime 6 group by datepart(hh,ReceiveTime) 7 order by datepart(hh,ReceiveTime)
如果想在where条件使用sum函数，通过having来实现：
select PrescCode from PrescriptionDetail group by PrescCode having sum(OutQuantity)>=sum(Quantity)
