Duplicate Emails

Desicription

Write a SQL query to find all duplicate emails in a table named Person.

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+----+---------+
| 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:

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

Note: All emails are in lowercase.

Solution

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SELECT DISTINCT P1.Email
AS Email
from Person P1, Person P2
WHERE P1.Email = P2.Email AND P1.Id != P2.Id