问题描述
https://leetcode.com/problems/customers-who-never-order/
解决思路
用LEFT JOIN通过ON的条件，将两个表连接，筛选出tb2中Id为空的，即为答案。
问题解惑
ON和WHERE的区别？
ON是连接条件；WHERE是筛选条件
代码
# Write your MySQL query statement below
SELECT Name as Customers
FROM Customers as tb1
LEFT JOIN Orders as tb2
on tb1.Id = tb2.CustomerId
WHERE tb2.Id is null;
