总计由多列

Question

我有服务，它有多个任务。每个任务都有一个特定向量的扣除。

我希望通过每个Vector_id和每个服务查询所有矢量扣除％。

例如，我想：

Service | Vector | Deduction % 
--------------------------------------- 
    SM  |  10  |  5 
    SM  |  11  |  10 
    .... 
    ES  |  10  |  5  
    .... 

我已经得到命令我希望通过总结扣除列，但不能按语句获取正确的组：

Select 
Service.name AS ServiceName, 
Task.name AS TaskName, 
Deduction.Vector_id AS DeductionVector, 
Deduction.deduction AS DeductionPercentage 
FROM 
Task JOIN Service ON 
Service.id = Task.Service_id 
JOIN Deduction ON 
Deduction.Task_id = Task.id  
ORDER BY ServiceName, DeductionVector; 

下面是各表正在使用和一些数据：http://www.sqlfiddle.com/#!9/ea5f70

Answer 1

试试这个：

Select 
    Service.name AS ServiceName, 
    Task.name AS TaskName, 
    Deduction.Vector_id AS DeductionVector, 
    SUM(Deduction.deduction) AS DeductionPercentage 
... 
GROUP BY Service.name, Task.name, Deduction.Vector_id 
... 

请注意，您应始终使用Group By您在Select中使用的所有列，但聚合值（例如COUNT或SUM）除外。