客户要求的每个类别的产品是什么？ NorthwindDB

Question

我试图解决这个问题而且我已经到了这个

SELECT 
    c.CategoryID, p.ProductID,p.ProductName, COUNT(OrderID) TotalV 
FROM 
    [Order Details] od
INNER JOIN 
    Products p ON od.ProductID = p.ProductID
INNER JOIN 
    Categories c ON c.CategoryID = p.CategoryID
INNER JOIN 
    (SELECT 
         t.CategoryID, MIN(TotalV) MinV 
     FROM
         (SELECT 
              Categories.CategoryID, Products.ProductID, 
              COUNT(OrderID) TotalV 
          FROM 
              [Order Details]
          JOIN 
              Products ON [Order Details].ProductID = Products.ProductID
          JOIN 
              Categories ON Categories.CategoryID = Products.CategoryID
          GROUP BY 
              Products.ProductID, Categories.CategoryID) t
    GROUP BY 
        t.CategoryID) n ON c.CategoryID = n.CategoryID
GROUP BY 
    c.CategoryID, p.ProductID, MinV, p.ProductName
HAVING 
    COUNT(OrderID) = MinV

结果：

CategoryID | ProductID |        ProductName         | TotalV
-----------| ----------| ---------------------------| ------ 
1          | 67        | Laughing Lumberjack Lager  | 10     
2          | 15        | Genen Shouyu               | 6
3          | 48        | Chocolade                  | 6
.            .                   .                     .
.            .                   .                     .
.            .                   .                     .

我不确定这是否是一个好方法，因为我使用了两次：

SELECT 
    Categories.CategoryID,Products.ProductID, COUNT(OrderID) TotalV 
FROM 
    [Order Details]
JOIN 
    Products ON [Order Details].ProductID = Products.ProductID
JOIN 
    Categories ON Categories.CategoryID = Products.CategoryID
GROUP BY 
    Products.ProductID, Categories.CategoryID

所以我认为可以有更好的方法来执行这个问题，任何帮助？