题目：196. Delete Duplicate Emails 1。建表
create table Person( Id int not null auto_increment, Email varchar(30) default null, primary key (Id) ) insert into Person(Email) values ('john@example.com'); insert into Person(Email) values ('john@example.com'); insert into Person(Email) values ('bob@example.com'); insert into Person(Email) values ('tom@example.com'); insert into Person(Email) values ('tom@example.com'); insert into Person(Email) values ('tom@example.com'); select * from Person;2。解答：
DELETE FROM Person WHERE Id NOT IN ( SELECT * FROM ( SELECT Min(Id) FROM Person GROUP BY Email ) tmp ) delete from Person where Id not in ( select Id from (select min(Id) as Id from Person group by Email ) tmp ); delete from Person where Id not in ( select Id from ( select min(Id) as Id from Person group by Email )as tmp ) DELETE p1 FROM Person p1, Person p2 WHERE p1.Email = p2.Email AND p1.Id > p2.Id;