重复数据

select user_name,over,count(*) from user1 group by user_name,over having count(*) > 1;

DELETE a FROM user1 a JOIN (
  SELECT user_name,COUNT(*),MAX(id) AS id FROM user1 GROUP BY user_name HAVING COUNT(*) > 1
) b ON a.user_name = b.user_name WHERE a.id < b.id;