Duplicate Emails-LeetCode_No.182

Description: Write a SQL query to find all duplicate emails in a table name Person.

+----+---------+
| Id | Email   |
+----+---------+
| 1  | [e-mail] |
| 2  | [e-mail] |
| 3  | [e-mail] |
+----+---------+

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

+---------+
| Email   |
+---------+
| [e-mail] |
+---------+

Note: All emails are in lowercase.

Solution:

SELECT
    Email
FROM
    (SELECT
        Email, count(Email) AS num 
     FROM
        Person 
     GROUP BY Email) result_set 
WHERE 
    result_set.num > 1;

or

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