力扣182. 查找重复的电子邮箱
https://leetcode-cn.com/problems/duplicate-emails/
编写一个 SQL 查询,查找 Person 表中所有重复的电子邮箱。
示例:
+----+---------+
| Id | Email |
+----+---------+
| 1 | [email protected] |
| 2 | [email protected] |
| 3 | [email protected] |
+----+---------+
根据以上输入,你的查询应返回以下结果:
+---------+
| Email |
+---------+
| [email protected] |
+---------+
说明:所有电子邮箱都是小写字母。
思路:先分组再筛选
使用 GROUP BY
和 HAVING
条件
# Write your MySQL query statement below
select Email
from person
group by email#分组
having count(email)>1;#筛选
group by + 没聚集的列
筛选having+ 聚集函数