SQL之删除重复数据

如果有相同数据的话保留相同数据id为最大的，删除其他的数据。

delete a        from user a        left join             (select username, count(id), Max(id) as id                 from user                 group by username                 having count(id) > 1) b        on a.username = b.username where a.id < b.id;