Question

以下是我在下面尝试查询的问题。

对于每个订单，列出订单号，订单日期，部件号，部件描述和项目构成订单的每个部分的类

数据库有一个Order_Line表，由order_num，Part_num，Num ordered和quoted_price组成。它还有一个order_num，order_date和Customer_num的订单表。此查询使用的第三个表是具有Part_num，description，On_Hand，Class，Warehouse和Price的part表。看来我必须加入所有三个表。这是我试过的查询。

Select Orders.Order_Num, Order_Date, Part.Part_Num , Description, Class 
From Orders, Customer, Part  
Where Orders.Order_Num = Order_Line.Order_Num
And  Order_Line.Part_Num = Part.Part_Num

Answer 1

Select *        --<-- use two part names here  
From       Customer
INNER JOIN Orders     ON Customer.CustomerID = Orders.CustomerID  --<-- Only guessing
INNER JOIN Order_Line ON Orders.Order_Num = Order_Line.Order_Num
INNER JOIN Part       ON Order_Line.Part_Num = Part.Part_Num

您还没有提到如何将查询中的订单加入到客户表中，这为您提供了两个表的笛卡尔积。

Answer 2

你错过了一张桌子，似乎在你的名单中有一张额外的桌子：

您可能正在尝试这样做：

Select Orders.Order_Num, Order_Date, Part.Part_Num , Description, Class 
From Orders
inner join part on 
 Order_Line.Part_Num = Part.Part_Num
inner join OrderLine on 
  Orders.Order_Num = Order_Line.Order_Num

- 无法判断哪些列'客户'表可以加入....

用SQL查询SQL问题

2 个答案: