Question

表[Orders] : OrderID(Primary Key), CustomerID
表[Order Details] : OrderID(Primary Key), ProductID(Primary Key), Discount
表[Customers] : CustomerID[Primary Key]

使用这三个表格，我想查询每个productID的最高折扣CustomerID。我需要ProductID，CustomerID和Discount的列。我怎么解决这个问题？真的很感激各种帮助。

我已尝试过以下脚本：

select ProductID, a.customerID, 
    (select MAX(discount) 
     from [Order Details] 
     where a.CustomerID=c.customerID
    )
from Orders a 
    join [Order Details]
        on a.OrderID=[Order Details].OrderID 
    join Customers c
        on a.CustomerID=c.CustomerID    
order by customerID

Answer 1

以下查询将以最大折扣为每位客户返回productid。请注意，如果针对特定客户，您有多个可能具有最高折扣的产品，我想要退回，那么您需要将ROW_NUMBER()替换为DENSE_RANK()

  WITH CTE AS 
    (SELECT ProductID, 
           o.CustomerID,
           Discount,
           ROW_NUMBER() OVER(PARTITION BY o.CustomerID ORDER BY Discount DESC) Row_num
    FROM [Order Details] od INNER JOIN Orders o
         ON od.OrderID= o.OrderID
    )
    SELECT ProductID, 
           CustomerID,
         Discount
    FROM CTE
    WHERE Row_num = 1

使用Northwind数据库和SQL Server的三个表之间的子查询

1 个答案: