SQL-是否通过子选择进行分组？

我有以下疑问：

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，它会将每小时的通话次数分组，但我想做的是将上午12点到7点之间的通话分组，然后将下午6点到12点之间的通话分组，因为在这些时间拨打的电话不多，所以在这些时间里，每小时拨打的电话次数似乎没有意义（因为它们不在营业时间）。这可能吗？

试试这样的方法

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

---

试试这样的

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

---

您可以使用

案例

将小时转换为时段：

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

---

您可以使用

案例

将小时转换为时段：

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

---

+1表示不必在select和group by中重复大小写。@BiffBaffBoff:表示排序，您可以使用（这是sql server语法）：=order by cast（当charindex（'-'，句点，1）>0时的大小写，然后使用子字符串（句点，1，charindex（'-'，句点，1）-1）否则句点结束为int）+1，因为不必在select和group by中重复大小写。@biffbaffoff:对于排序，您可以使用（这是sql server语法）：=按类型转换的顺序（当charindex（'-'，句点，1）>0时，则为子字符串（句点，1，charindex（'-'，句点，1）-1），否则句点以int结束）