https://leetcode-cn.com/problems/customers-who-never-order/
从不订购的客户
select Customers.Name as Customers from Customers where Customers.Id not in (select Orders.CustomerId from Orders);
个人理解：作为一个sql入门白痴，not in是个好东西
原文：https://www.cnblogs.com/newliu/p/11613906.html