select grade from sc where cno=’1002’)
select top 3 sno from sc group by sno order by avg(grade)desc a:select*from student where sdept=’JSJ’ and sage>19
b:select*from student where sdept=’JSJ’ except select* from student where sage<19 select student.sno,sname from student,sc where cno=’1001’ and grade>90 union select sno,sname from student where sno in （ select sno from sc group by sno having avg(grade)>85)
select sno from student where sno not in(select sno from sc x where grade< ( select avg(grade) from sc where cno=x.cno) ) select sname from student x where sage> (
select avg(sage) from student where sdept=x.sdept)