两个SQL问题记录下

1、有表SCcore:ID,Name,Course,Score 删除ID不同,Name,Course,Score均相同的记录

编译不通过： delete from (select ROW_NUMBER() over(partition by Name,Cname,score order by ID) num from SCScore) T where num<>1

这样写可以： delete from SCScore where id in(select ID from (select ID,ROW_NUMBER() over(partition by Name,Cname,score order by ID) num from SCScore) T where num<>1)

不清楚为什么？

2、用case when增加一列

select ID,Name,CName,Score,case when Score>60 then '及格' else  '不及格' end as 评级 from SCScore