学生表（包括学号，姓名，性别，年龄，所在系）
create table student( Sno char(9) primary key, Sname char(20) unique, Ssex char(2), Sage smallint, Sdept char(20) );
数值插入:
insert into STUDENT(Sno,Sname,Ssex,Sage,Sdept) values('201215121','李勇','男',20,'CS'); insert into STUDENT(Sno,Sname,Ssex,Sage,Sdept) values('201215122','刘晨','女',19,'CS'); insert into STUDENT(Sno,Sname,Ssex,Sage,Sdept) values('201215123','王敏','女',19,'MA'); insert into STUDENT(Sno,Sname,Ssex,Sage,Sdept) values('201215125','张立','男',19,'IS');
课程表（包括课程号，课程名，先行课，学分）
create table course( Cno char(4)primary key, Cname char(40), Cpno char(4), Ccredit SMALLINT, foreign key(Cpno) references course(Cno) );
数值插入：
insert into COURSE(Cno,Cname)values('1','数据库'); insert into COURSE(Cno,Cname)values('2','数学'); insert into COURSE(Cno,Cname)values('3','信息系统'); insert into COURSE(Cno,Cname)values('4','操作系统'); insert into COURSE(Cno,Cname)values('5','数据结构'); insert into COURSE(Cno,Cname)values('6','数据处理'); insert into COURSE(Cno,Cname)values('7','PASCAL语言');
选课表（包括学号，课程号，成绩）
create table SC( Sno char(9), Cno char(4), Grade smallint, primary key(Sno,Cno),//主键是两个外键 foreign key(Sno) references student(Sno), foreign key(Cno) references course(Cno) );
数值插入:
insert into SC(Sno,Cno,Grade) values('201215121','1',92); insert into SC(Sno,Cno,Grade) values('201215121','2',85); insert into SC(Sno,Cno,Grade) values('201215121','3',88); insert into SC(Sno,Cno,Grade) values('201215122','2',90); insert into SC(Sno,Cno,Grade) values('201215122','3',80);
