Question

我有一个名为windowLightStatusBar的sql server 2014表，其中包含此项

Machines

还有另一个名为ID || ProjectName || MachineTypeID || MachineName ---------------------------------------------------------------------- 1 || project1 || 1 || m1 1 || project2 || 2 || m2 1 || project1 || 2 || m3 1 || project2 || 1 || m4 1 || project1 || 2 || m5的表，其中包含这些项目

MachineTypes

所有人都想用此输出写一个查询

Id || Title 
-------------------
1  || BigMachine
2  || SmallMachine

我希望有可能

Answer 1

编辑（在您发布示例之后）

此查询应为您提供所需的结果。我很确定这个问题的解决方案已经在这里@ SO。

链接到sqlfiddle：http://www.sqlfiddle.com/#!9/e3ef7a/1

select ProjectName, 
       sum(case when MachineTypeID=1 then 1 else 0 end) as BigCount, 
       sum(case when MachineTypeID=2 then 1 else 0 end) as SmallCount
from Machines group by ProjectName

Answer 2

尝试此查询：

declare @t1 table(ID int, ProjectName varchar(10), MachineTypeID int, MachineName varchar(5));
insert into @t1 values
(1, 'project1',1, 'm1'),
(1, 'project2',2, 'm2'),
(1, 'project1',2, 'm3'),
(1, 'project2',1, 'm4'),
(1, 'project1',2, 'm5');

declare @t2 table (Id int, Title varchar(20));
insert into @t2 values
(1, 'BigMachine'),
(2, 'SmallMachine');

select ProjectName,
       max(case when MachineTypeId = 1 then cnt end) BigMachineCount,
       max(case when MachineTypeId = 2 then cnt end) SmallMachineCount
from (
    select ProjectName, MachineTypeId, count(*) cnt from @t1
    group by ProjectName, MachineTypeId
) a group by ProjectName

计算项目计数并作为列返回

2 个答案: