LeetCode183——从不订购的客户
我的LeetCode代码仓:https://github.com/617076674/LeetCode
原题链接:https://leetcode-cn.com/problems/customers-who-never-order/description/
题目描述:
知识点:子查询
思路:利用子查询在Orders表中寻找各个顾客的Id在CustomerId中出现的次数
时间复杂度是O(nm),其中n为Customers表中的记录数,m为Orders表中的记录数。
SQL语句:
SELECT Name AS Customers FROM Customers WHERE (SELECT COUNT(1) FROM Orders WHERE Orders.CustomerId = Customers.Id) = 0;
LeetCode解题报告: