Question

我有一个SQL Server 2008数据库。该数据库有两个相关的表：Customer和Order。我的表看起来像这样：

Customer
--------
ID
FirstName
LastName

Order
-----
ID
CustomerID
Amount
ShipDate

我需要删除所有没有订单的客户。我无法弄清楚这样做的最佳方法。谁能告诉我怎么做？ NOT部分是让我不断的。最初我使用的是“IN”，但这让我很难过。

感谢您的帮助！

Answer 1

使用子查询和NOT EXISTS，而不是使用IN运算符，如：

DELETE Customers
FROM   Customers c
WHERE NOT EXISTS (
    SELECT 1
    FROM Orders o
    WHERE o.CustomerID = c.ID
)

Answer 2

DELETE Customer 
WHERE ID IN
(
    SELECT Customer.ID
    FROM Customer 
    LEFT JOIN Order ON
        Customer.ID = ORder.CustomerID
    WHERE ORder.CustomerID IS NULL
)

Answer 3

Delete from Customer 
WHERE ID in 
(
   SELECT C.ID
     FROM Customer C
   Left Outer Join Order O ON C.ID = O.CustomerId
   WHERE O.ID IS NULL
)

删除未在SQL中连接的记录

3 个答案: