Question

Formatted question description: https://leetcode.ca/all/182.html

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.

Algorithm

Group by…Having Count(*)…

Code

SQL

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

--

SELECT DISTINCT p1.Email FROM Person p1
JOIN Person p2 ON p1.Email = p2.Email
WHERE p1.Id <> p2.Id;

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