SQL Server：按两列分组，并将第三列与两组的分叉相加

Question

我正在创建一个发票系统，我需要使用两个过滤器（即month 和category_of_service）来获取total_amount 的总和

到目前为止，我可以根据两个过滤器使用 GROUP BY 子句，但我的 SUM 是作为整体计算的，而不是根据组。

我已经提到了各种问题，但无法找到我的解决方案。

MySQL: Group by two columns and sum

month | category_of_service | total_amount
------|---------------------|-------------
12    | EB                  | 1000
12    | EB                  | 1200
12    | DG                  | 1500
12    | DG                  | 2000

我能做的是

month | category_of_service | total_amount
------|---------------------|-------------
12    | EB                  | 5700
12    | DG                  | 5700

我真正想要的是

month | category_of_service | total_amount
------|---------------------|-------------
12    | EB                  | 2200
12    | DG                  | 3500

注意：有多个months和category_of_services

我使用的查询是：

SELECT 
    month, category_of_service, SUM(total_amount) AS TotalAmount
FROM  
    dbo.report
GROUP BY 
    month, category_of_service

这是我的输出截图：

enter image description here

Answer 1

 ;With Cte([month] , category_of_service , total_amount)
AS
(
SELECT 12    , 'EB', 1000 Union all
SELECT 12    , 'EB', 1200 Union all
SELECT 12    , 'DG', 1500 Union all
SELECT 12    , 'DG', 2000 
)
, Result
AS
(
SELECT * ,ROW_NUMBER()OVER(PARTITION by total_amount ORDER BY [month] desc)  AS Seq FROM
(
SELECT [month] , category_of_service ,Sum(total_amount)OVER(PARTITION BY [month],category_of_service ORDER BY [month])AS total_amount  FROM Cte
)dt
)
SELECT [month] , category_of_service , total_amount FROM Result WHERE seq=1

---

输出

month | category_of_service | total_amount
------|---------------------|-------------
12    | EB                  | 2200
12    | DG                  | 3500