duplicate_emails.sql

-- Table: Person
-- +-------------+---------+
-- | Column Name | Type    |
-- +-------------+---------+
-- | id          | int     |
-- | email       | varchar |
-- +-------------+---------+
-- id is the primary key (column with unique values) for this table.
-- Each row of this table contains an email. The emails will not contain uppercase letters.
 
-- Write a solution to report all the duplicate emails. Note that it's guaranteed that the email field is not NULL.

-- Return the result table in any order.

-- The result format is in the following example.
-- Example 1:

-- Input: 
-- Person table:
-- +----+---------+
-- | id | email   |
-- +----+---------+
-- | 1  | a@b.com |
-- | 2  | c@d.com |
-- | 3  | a@b.com |
-- +----+---------+

-- Output: 
-- +---------+
-- | Email   |
-- +---------+
-- | a@b.com |
-- +---------+
-- Explanation: a@b.com is repeated two times.
SELECT email FROM Person
GROUP BY email
HAVING COUNT(email) > 1;