这个查询哪错了！
create view se1(s_sno,s_sname,c_num,s_avg_grade)
as select sc.sno,s.sname,count(cno),avg(grade)
from s,sc
where s.sno=sc.sno
group by sno,cno
提示说：列名 'sno' 不明确。
[解决办法]
create view se1(s_sno,s_sname,c_num,s_avg_grade)
as select sc.sno,s.sname,count(cno),avg(grade)
from s,sc
where s.sno=sc.sno
group by sc.sno,cno
[解决办法]
