text: /*
  https://leetcode.com/problems/duplicate-emails/
  182. Duplicate Emails
  Easy
  SQL Schema>
  Create table If Not Exists Person (Id int, Email varchar(255))
  Truncate table Person
  insert into Person (Id, Email) values ('1', 'a@b.com')
  insert into Person (Id, Email) values ('2', 'c@d.com')
  insert into Person (Id, Email) values ('3', 'a@b.com')
  ---------------------------------------------------------------
  
  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.
  
  Solution:
  # Time:  O(n^2)
  # Space: O(n)
  */
  
  SELECT Email FROM Person GROUP BY Email HAVING COUNT(*) > 1;
  -- OR
  select a.Email
  from Person a
  group by a.Email
  having count(a.Email) > 1
  ;
  