Question

我该如何选择

| Customer_name | Num_of_AllTime_Orders | Num_of_different_Products_That_Customer_Ordered |

当每个数据来自不同表时作为表？

我试图计算客户数量，加入表格并进行分组...但是没有运气。

SELECT CompanyName, count(Customer_ID) from dbo.CUSTOMERS join dbo.ORDERS on CUSTOMERS.Customer_ID=ORDERS.CustomerID

Customers_Table：

CustomerID | Customer_Name

Orders_Table：

OrderID| Customer_ID

Order_Detail_Table：

OrderID| Product_ID |

我希望具有这些列的表的输出：

1. Customer_Name
2. Num_of_AllTime_Orders  - how many orders that costumer made?
3. Num_of_different_Products_That_Customer_Ordered - how many different products that customer ordered?

Answer 1

Select CUSTOMERS.Customer_Name
    ,count(distinct ORDERS.OrderID) as Num_of_AllTime_Orders
    ,count(distinct Order_Detail_Table.Product_ID) as Num_of_different_Products_That_Customer_Ordered   
from dbo.CUSTOMERS 
    join dbo.ORDERS on CUSTOMERS.CustomerID = ORDERS.Customer_ID
    join dbo.Order_Detail_Table on ORDERS.OrderID = Order_Detail_Table.OrderID
group by CUSTOMERS.Customer_Name

Answer 2

SELECT Company_Name = C.CompanyName, NumOfOrders = COUNT (DISTINCT O.OrderID), NumOfProducts = COUNT (DISTINCT OD.ProductID)
FROM dbo.CUSTOMERS AS C JOIN ORDERS AS O ON C.Customer_ID=O.CustomerID JOIN ORDERDETAILS AS OD ON OD.OrderID=O.OrderID
GROUP BY C.CompanyName
ORDER BY 1

从多个表中选择不同的数据

2 个答案: