sql - 自定义分组依据并将一些记录放在一个组中

Question

请考虑数据：

 Id          Group            Value
 -----------------------------------
 1            1                10
 2            1                12
 3            1                10
 4            2                90
 5            2                10
 6            3                30
 7            4                12
 8            4                11
 9            5                10
 10           5                11

我想将Group By这些数据1,2,3放在一个组中并4,5放在另一组中。我怎么能做到这一点SQL Server？

谢谢

---

编辑 1)

我想要这个结果：

Groups                              Count
-----------------------------------------
Group for 1,2,3                       6
Group for 4,5                         4

Answer 1

这也可以做你想要的：

SELECT 'Group for 1,2,3' AS GROUPS
   ,   COUNT(Id) AS Count
FROM Foo
WHERE [Group] IN (1,2,3)

UNION ALL

SELECT 'Group for 4,5' AS GROUPS
   ,   COUNT(Id) AS Count
FROM Foo
WHERE [Group] IN (4,5)

http://sqlfiddle.com/#!6/cdb82/2/0

当然，这只有在您知道您想要哪些组时才有效。

Answer 2

我正在使用outer apply，因此您不会将代码复制到组中

select
    C.Group_Name, count(*)
from Table1
    outer apply
    (
        select
            case
                when C.[Group] in (1, 2, 3) then 'Group for 1, 2, 3'
                when C.[Group] in (4, 5) then 'Group for 4, 5'
            end as Group_Name
    ) as C
group by C.Group_Name

你也可以使用子查询

select
    C.Group_Name, count(*)
from 
(
    select
        case
            when T.[Group] in (1, 2, 3) then 'Group for 1, 2, 3'
            when T.[Group] in (4, 5) then 'Group for 4, 5'
        end as Group_Name,
        T.Value,
        T.Id
    from Table1 as T
) as C
group by C.Group_Name