MYSQL数据库删除表中重复数据只保留一条

delete from think_user where id in (select id from (select  max(id) as id,count(username) as count from think_user group by username having count >1 order by count desc) as tab )

其中think_user为表名，username为其中一个字段

网上找了很多方法，测试结果只有这好用，不知道是不是数据库版本问题。