[LeetCode] [SQL]: 182: Duplicate Emails

题目：

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.

分析：分组（Group by） 加 统计（Count）即可

SQL

SELECT Email
FROM Person
GROUP BY Email Having count(*)>1