[LeetCode]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 |
+---------+

解题：按照Email分组，然后找出id出现次数超过1的Email。
SQL语句使用group by 和 having 实现：

select Email from Person group by Email having count(id) > 1;