create table student
(
sno NUMBER(5) not null,
sname VARCHAR2(20),
idcard VARCHAR2(18),
createtime DATE default SYSDATE,
nno NUMBER(2),
constraint PK_STUDENT primary key (sno)
);
create table course
(
cno NUMBER(5) not null,
cname VARCHAR2(20),
constraint PK_COURSE primary key (cno)
);
create table nativeplace
(
nno NUMBER(2) not null,
np_name VARCHAR2(20),
constraint PK_NATIVEPLACE primary key (nno)
);
create table sc
(
sno NUMBER(5) not null,
cno NUMBER(5) not null,
grade NUMBER(4,1),
constraint PK_SC primary key (sno, cno)
);
alter table sc add constraint fk_sc_sno foreign key (sno) references student (sno) on delete cascade;
alter table sc add constraint fk_sc_cno foreign key (cno) references course (cno);
alter table student add constraint fk_student foreign key (nno) references nativeplace (nno) on delete set null;
insert into nativeplace values(1,‘heilongjiang‘);
insert into nativeplace values(2,‘jilin‘);
insert into nativeplace values(3,‘liaoning‘);
insert into nativeplace values(4,‘beijing‘);
insert into course VALUES(1,‘Oracle‘);
insert into course VALUES(2,‘Java‘);
insert into course VALUES(3,‘C++‘);
insert into student values(1,‘zhangsan‘,‘123456789123456780‘,default,1);
insert into student values(2,‘lisi‘,‘123456789123456781‘,default,2);
insert into student values(3,‘wangwu‘,‘123456789123456782‘,default,3);
insert into student values(4,‘zhaoliu‘,‘123456789123456783‘,default,4);
insert into sc values(1,1,91);
insert into sc values(1,2,92);
insert into sc values(1,3,93);
insert into sc values(2,1,88);
insert into sc values(2,2,77);
insert into sc values(2,3,99);
insert into sc values(3,1,65);
insert into sc values(3,2,75);
insert into sc values(3,3,85);
insert into sc values(4,1,80);
insert into sc values(4,2,88);
insert into sc values(4,3,89);
commit;
alter table sc drop constraint fk_sc_sno;
alter table sc drop constraint fk_sc_cno;
alter table student drop constraint fk_student;
drop table course cascade constraints;
drop table nativeplace cascade constraints;
drop table sc cascade constraints;
drop table student cascade constraints;