//一个学生表
//一个课程表
//一个选课表
//就这么简单,谁帮我改改,谢谢了,才学Oracle!

create table Student(
sname varchar(10),
sid char(4),
ssex varchar(4),
sdept varchar(10),
primary key(sid),
check (ssex in ('男','女'))
);
create table Class(
cname varchar(10),
cid varchar(4),
xuefen varchar(2)
);
create table Sel(
sid char(4),
sname varchar(10),
cid varchar(4),
cname varchar(10),
chengji varchar(3),
foreign key(sid,cid) reference Student(sid),Class(cid)
);

insert into Student values('张三','0001','男','计算机系');
insert into Class values('数学','0012','5');