Question

我想选择每个客户购买的最昂贵的产品，但我有3个表中的信息：客户，购买，产品价格。

表格如下：

客户：

Customer_ID | Customer_Name

购买：

Customer_ID | Product_ID

ProductPrices：

Product_ID | Price

我正在运行的是：

SELECT  
Customer_Name, max(Price), Purchases.Product_ID
            FROM Customers 
            LEFT JOIN Purchases 
            ON Customers.Customer_ID=Purchases.Customer_ID
            LEFT JOIN ProductPrices
            ON Purchases.Product_ID=ProductPrices.Product_ID
                        GROUP BY Customer_Name
                        ORDER BY ABS(Price) DESC
                        ;

我得到的输出是名称和最高购买正确，但product_id是第一个，与最高价格无关。

你能帮助我发现我做错了吗？

编辑：

为了让您更轻松，我创建了这个：

http://sqlfiddle.com/#!2/db7f9/1

Answer 1

试试这个：

select distinct c.Customer_Name,pp.Product_Id,m.Price
from 
  (select Customer_ID,max(Price) as Price
  from Purchases p join ProductPrices pp on (p.Product_ID=pp.Product_ID)
  group by Customer_ID) m
join Customers c on (m.Customer_ID=c.Customer_ID)
join ProductPrices pp on (pp.Price=m.Price)
join Purchases p on (m.Customer_ID=p.Customer_ID and p.Product_ID=pp.Product_ID)

注意：如果客户购买了多个价格相同的产品，这将为每位客户提供多个行。

Answer 2

试试这个

    SELECT Customer_Name, max(Price) price , Product_ID FROM (
 SELECT  
Customer_Name, Price, Purchases.Product_ID
        FROM Customers 
        INNER JOIN Purchases 
        ON Customers.Customer_ID=Purchases.Customer_ID
        INNER JOIN ProductPrices
        ON Purchases.Product_ID=ProductPrices.Product_ID


                    ORDER BY ABS(Price) DESC
)t

GROUP BY Customer_Name

DEMO HERE

输出：

  CUSTOMER_NAME     PRICE   PRODUCT_ID
     John           30000   3
     Kate           30000   3
     Peter          20000   2

从mysql中的不同表中选择最大值

2 个答案: