LeetCode: 182. Duplicate Emails

LeetCode: 182. Duplicate Emails

Write a SQL query to find all duplicate emails in a table named Person.

+----+---------+
| Id | Email   |
+----+---------+
| 1  | a@b.com |
| 2  | c@d.com |
| 3  | a@b.com |
+----+---------+

For example, your query should return the following for the above table:

+---------+
| Email   |
+---------+
| a@b.com |
+---------+

Note: All emails are in lowercase.

解题思路

根据 Email 进行分组， 数据条数大于 1 的组的 Email 有重复的。

• GROUP BY: 对表进行分组
• HAVING: 为聚合结果指定条件

AC 代码

SELECT DISTINCT Email 
FROM Person
GROUP BY Email
HAVING COUNT(*) > 1