加权平均访问查询

Question

背景：我有下表，其中包含服装品牌名称、已售品牌名称的数量、该品牌名称带来的收入以及该品牌名称的每单位销售平均值。

Quantity Brand       Revenue       Rev_Per_Brand
1820     CMD         $13,519.50    $7.43
791      ATL         $8,997.00      $11.37
335      WHBM        $4,988.00      $14.89
320      CH          $4,593.50     $14.35
233      AT          $3,207.50     $13.77

目标：按品牌销量计算加权平均收入。

我现在拥有的：

SELECT 
COUNT(*) AS [Quantity], 
Sales.Description AS Brand, 
FORMAT(SUM(Sales.Amt),"Currency") AS Revenue, 
Format(SUM(Sales.Amt)/COUNT(*), "Currency") AS Rev_Per_Brand, 

SUM(Sales.Amt)*(COUNT(*)/SUM(COUNT(*))) AS [wAvg_Rev_Per_Brand]

FROM Sales
WHERE Sales.Date > DateAdd("m",-1,NOW())
AND "This query lists brands that have sold in the past 1 month from today's date and returns the revenue received from them" <> ""
GROUP BY Sales.Description
ORDER BY COUNT(*) DESC;

问题：我收到 cannot have aggregate function in expression 错误，我猜它可能在上面的 SUM(COUNT(*)) 部分。

我只是想计算特定品牌的数量，而不是所有已售品牌的总数量（总和）。谁能告诉我我做错了什么？

谢谢您，我非常感谢您提前提供的任何帮助。

Answer 1

你不能双重聚合，即SUM(COUNT(*))你必须在一个单独的子查询中计算，

将您的查询更改为：

SELECT 
COUNT(*) AS [Quantity], 
Sales.Description AS Brand, 
FORMAT(SUM(Sales.Amt),"Currency") AS Revenue, 
Format(SUM(Sales.Amt)/COUNT(*), "Currency") AS Rev_Per_Brand, 

SUM(Sales.Amt)*(COUNT(*)/(SELECT Count(*) FROM sales)) AS [wAvg_Rev_Per_Brand]

FROM Sales
WHERE Sales.Date > DateAdd("m",-1,NOW())
AND "This query lists brands that have sold in the past 1 month from today's date and returns the revenue received from them" <> ""
GROUP BY Sales.Description
ORDER BY COUNT(*) DESC;