数据库实验指导书第一次实验代码

create table Student

(


sno char(5) primary key,


sname varchar(10) unique,


ssex char(2) not null,


sage number(3) default 0,


sdept varchar(10)


);


create table Course
(
cno char(1) primary key,
cname varchar(15) not null,
cpno char(1),
ccredit number(1)
);

create table SC
(
sno char(5) primary key,
cno char(1) not null,
crade number(3)
);

desc Student;
desc Course;
desc SC;

select * from Student;
select * from Course;
select * from SC;

alter table Student add snp varchar(20);

alter table Student add sintime date;


alter table Course modify cno char(2);


alter table Course modify cpno char(2);


alter table SC modify cno char(2);


alter table Student drop unique(sname);