text: -- https://leetcode.com/problems/delete-duplicate-emails/
  --
  -- Write a SQL query to delete all duplicate email entries in a table named
  -- Person, keeping only unique emails based on its smallest Id.
  --
  --     +----+------------------+
  --     | Id | Email            |
  --     +----+------------------+
  --     | 1  | john@example.com |
  --     | 2  | bob@example.com  |
  --     | 3  | john@example.com |
  --     +----+------------------+
  --
  -- For example, after running your query, the above Person table should have
  -- the following rows:
  --
  --     +----+------------------+
  --     | Id | Email            |
  --     +----+------------------+
  --     | 1  | john@example.com |
  --     | 2  | bob@example.com  |
  --     +----+------------------+
  
  
  DELETE FROM Person
   WHERE Id NOT IN (SELECT s.SmallestId
                      FROM (SELECT MIN(Id) AS SmallestId
                              FROM Person
                          GROUP BY Email
                      ) AS s
                   );
  