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. 用exists

1 select distinct Email from Person p1 where exists (select Id from Person p2 where p1.Email = p2.Email and p1.Id != p2.Id);

用group by

1 select Email from Person group by Email having count(Email) > 1;