text: /*
  196. Delete Duplicate Emails
  
  https://leetcode-cn.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.
  
  
  Truncate table Person;
  insert into Person (Id, Email) values ('1', 'john@example.com');
  insert into Person (Id, Email) values ('2', 'bob@example.com');
  insert into Person (Id, Email) values ('3', 'john@example.com');
  */
  delete l from Person as l, Person as r where l.Email = r.Email and l.Id > r.Id
  