drop table student cascade;
create table student (
	gnum integer,
	cnum integer,
	num integer check(num between 1 and 40),
	name text not null,
	gender integer not null check(gender in(1, 2)),
	blood varchar(2) not null,
	score integer check(score between 0 and 100),
	primary key(gnum, cnum, num)
);