从不订购的客户

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题目：

题解：

1、使用左连接

• 解题思路：

  • 

• sql语句：

  select a.Name as Customers
  from Customers as a
  left join Orders as b 
  on a.Id = b.CustomerId
  where b.CustomerId is null;

2、使用子查询和 NOT IN 子句

• sql语句：

  select a.Name as Customers
  from Customers as a
  where a.id not in 
  (
      select CustomerId from Orders
  );