[SQL]LeetCode183. 从不订购的客户 | Customers Who Never Order
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➤微信公众号：山青咏芝（shanqingyongzhi）
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Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.
Table: Customers.
+----+-------+ | Id | Name | +----+-------+ | 1 | Joe | | 2 | Henry | | 3 | Sam | | 4 | Max | +----+-------+
Table: Orders.
+----+------------+ | Id | CustomerId | +----+------------+ | 1 | 3 | | 2 | 1 | +----+------------+
Using the above tables as example, return the following:
+-----------+ | Customers | +-----------+ | Henry | | Max | +-----------+
某网站包含两个表，Customers 表和 Orders 表。编写一个 SQL 查询，找出所有从不订购任何东西的客户。
Customers 表：
+----+-------+ | Id | Name | +----+-------+ | 1 | Joe | | 2 | Henry | | 3 | Sam | | 4 | Max | +----+-------+
Orders 表：
+----+------------+ | Id | CustomerId | +----+------------+ | 1 | 3 | | 2 | 1 | +----+------------+
例如给定上述表格，你的查询应返回：
+-----------+ | Customers | +-----------+ | Henry | | Max | +-----------+
方法：使用子查询和NOT IN子句
算法：如果我们有一个订购过的客户列表，很容易知道谁从未订购过。
我们可以使用以下代码来获取此类列表。
select customerid from orders;
然后，我们可以NOT IN用来查询不在此列表中的客户。
1 select customers.name as 'Customers' 2 from customers 3 where customers.id not in 4 ( 5 select customerid from orders 6 );
222ms
1 # Write your MySQL query statement below 2 SELECT Name as 'Customers' from Customers where Id not in (select CustomerId from Orders)
