【MySql】查找重复的电子邮箱

## 182.编写一个 SQL 查询，查找 Person 表中所有重复的电子邮箱。

person表中数据：

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

只查询重复的值：

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

查询结果：

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

查询重复的值及重复数量：

select Email,count(*) as count from person group by Email having count>1;

查询结果为：

+---------+-------+
| Email   | count |
+---------+-------+
| a@b.com |     2 |
+---------+-------+