面试题中经常遇到的SQL题：删除重复数据，保留其中一条

---删除重复数据
delete from Permission
---找出拥有相同数据的记录
where Name in (select Name from Permission group by Name having COUNT(Name)>1)
---除了最小ID号的数据保留，其他的删除 (也可以用max(id))
and ID not in (select min(ID) from Permission group by Name having COUNT(Name)>1)