從總計中查找每一行的平均值

Question

我有以下幾欄的銷售表sale

sale_id | 部門| gross_amount

我需要從總銷售額中找到每個部門的平均銷售額

例如：- 表格

sale_id     Department     gross_amount
  1            A             10
  2            B             30
  3            A             25
  4            c              5

Desired output

Department               Gross_amount     avg
  A                          35            50       --(35/70)*100
  B                          30            42.86    --(30/70)*100
  C                          5             7.14     --(5/70) *100

即是dept_avg =（dept_total /總數）* 100例如：-A的dept_total總數= 35總數= A + B + C = 35 + 30 + 5 = 70

我最多可以找到Gross_amount

select Department ,sum(si.GrossPrice)  gross_amt
from Sale si
group by Department 
order by Department

為了獲得平均值，我嘗試按照

 select Department ,sum(si.GrossPrice) gross_amt,
    AVG(sum(si.GrossPrice)) avg
    from Sale si
    group by Department 
    order by Department

這給我一個錯誤

無法對包含聚合或子查詢的表達式執行聚合功能。

另外，我不確定我可以通過上述查詢獲得預期的平均值。 我怎么能達到同樣的目的。

Answer 1

將分組的總和除以總和：

SqlFiddleDemo

SELECT Department ,
     [Gross_amount] = SUM(gross_amount),
     [avg] = ROUND(CAST(SUM(gross_amount) AS DECIMAL(10,2))/
                   CAST((SELECT SUM(gross_amount) FROM tab) AS DECIMAL(10,2)) * 100
             ,2)
FROM tab
GROUP BY Department 
ORDER BY Department

Answer 2

如果您希望每個部門在總部門中所占的比例，我建議使用窗口函數：

SELECT Department, SUM(gross_amount) as gross_amount
       SUM(gross_amount)*100.0 / SUM(SUM(gross_amount)) over () as propotion
FROM tab
GROUP BY Department 
ORDER BY Department;