mysql删除重复行的实现方法

 create table relation( id int primary key auto_increment, userId int not null, fanId int not null );

insert into relation(userId,fanId) values(1,1) ,(1,1) ,(1,1), (2,2),(2,2) ,(3,3),(3,3);

delete t from relation sjoin relation t using(userId,fanId)where s.id<t.id;