This query will give us John, Sam, Tom, Tom because they all have the same email.
However, what I want is to get duplicates with the same email and name.
That is, I want to get "Tom", "Tom".
There are many ways to do this,
one of them below,
SELECT a.* FROM users a JOIN (SELECT username, email, COUNT(*) FROM users GROUP BY username, email HAVING count(*) > 1 ) b ON a.username = b.username AND a.email = b.email ORDER BY a.email