sql - SQL - 使用子选择分组？

Question

我有以下查询：

SELECT COUNT(DATEPART(hh, CallStart)), DATEPART(hh, CallStart) as 'Hour'
  FROM PhoneSystemLog 
 WHERE MONTH(CallStart) = @Month and YEAR(CallStart) = @Year 
 GROUP BY DATEPART(hh, CallStart)

这很好，它会将每小时拨打的电话数量分组，但我想做的是然后将上午 12 点至上午 7 点之间的呼叫分组，将下午 6 点至上午 12 点之间的呼叫分组，因为拨打的电话并不多在那些时候，因此在这些时间里每小时拨打电话的次数似乎毫无意义（因为他们不在营业时间）。这可能吗？

Answer 1

您可以使用 acase将小时转换为期间：

select  Period
,       count(*) as Calls
from    (
        select  case 
                when datepart(hh, CallStart) between 0 and 7 then '1-7'
                when datepart(hh, CallStart) between 18 and 23 then '18-24'
                else cast(datepart(hh, CallStart) as varchar(2))
                end as Period
        from    PhoneSystemLog
        where   MONTH(CallStart) = @Month 
                and YEAR(CallStart) = @Year 
        ) as SubQueryAlias
group by
        Period

Answer 2

尝试这样的事情

select count(DATEPART(hh, CallStart)), 
    CASE 
    when DATEPART(hh, callstart) between 0 to 7 then '12:00AM-7AM'
    when DATEPART(hh, callstart) between 18 to 23 then '06PM-12AM'
    END
as 'hour' from PhoneSystemLog  
where MONTH(callstart) = @Month and YEAR(callstart) = @Year  
group by 
    CASE 
    when DATEPART(hh, callstart) between 0 to 7 then '12:00AM-7AM'
    when DATEPART(hh, callstart) between 18 to 23 then '06PM-12AM'
    END