drop view student_v;
create view student_v as
	select s.gnum, g.color, s.cnum, c.charge, s.num, s.name, s.gender, s.blood, s.score
		from grade g, class c, student s
		where c.gnum = g.num and (s.gnum, s.cnum) = (c.gnum, c.num)
		order by g.num, c.num, s.num
;