select Sage from Student where Sname='张立'
select Student.Sname SC.Grade from Student link SC on Student.Sno=SC.Sno where SC.Grade>=60 order by SC.Grade asc
GRANT select on Course to 张三
select Student.Sno,Student.Sname from Student where Student.Sno in
(select top 1 SC.Grade from SC link Course on SC.Cno=Course.Cno where Course.Cname='操作系统' order by SC.Grade desc)