SUM（）数据基于另一列数据

Question

我有一个SQL表

Project ID  Employee ID   Total Days 

1     100     1 
1     100     1 
1     100     2 
1     100     6 
1     200     8 
1     200     2 

现在我需要这个表看起来像

Project ID  Employee ID   Total Days 

1     100     10 
1     200     10 

由于亚姆新的SQL，我是根据上述条件，很少使用SUM（）。

Answer 1

这里有两种方法

Declare @t Table(ProjectId Int, EmployeeId Int,TotalDays Int) 
Insert Into @t Values(1,100,1),(1,100,1),(1,100,2),(1,100,6),(1,200,8),(1,200,2) 

Approach1：

Select ProjectId,EmployeeId,TotalDays = Sum(TotalDays) 
From @t 
Group By ProjectId,EmployeeId 

Approach2：

;With Cte As(
Select 
    ProjectId 
    ,EmployeeId 
    ,TotalDays = Sum(TotalDays) Over(Partition By EmployeeId) 
    ,Rn = Row_Number() Over(Partition By EmployeeId Order By EmployeeId) 
From @t) 
Select ProjectId,EmployeeId,TotalDays 
From Cte Where Rn = 1 

结果

ProjectId EmployeeId TotalDays 
1   100  10 
1   200  10 

Answer 2

以下查询产生两列：EmployeeID,totalDays。

SELECT EmployeeID, SUM(totalDays) totalDays 
FROM tableName 
GROUP BY EmployeeID 

跟进的问题：为什么是你想要的结果projectId被1 and 2？

Answer 3

select min("Project ID")as 'Project ID',"Employee ID" 
    , SUM("Total Days") as 'Total Days' 
from table1 
group by "Employee ID"