一、题目
Customers Who Never Order
二、个人思考
1）乍眼一看不难，但是陷阱在答案还替换了表名，最基本的答案是按照题目的逻辑走：
select Customers.Name as Customers from Customers where Id not in (select distinct CustomerId from Orders);
2）表名的修改也可以这个样子改
select Name Customers from Customers where id not in (select DISTINCT CustomerId from Orders);
