建表

CREATE TABLE Student      

      (Sno   CHAR(9) PRIMARY KEY,              

  Sname CHAR(20) UNIQUE,         

       Ssex    CHAR(2),

               Sage   SMALLINT,

               Sdept  CHAR(20)

);

insert into student values('201215121','李勇','男',20,'CS');

insert into student values('201215122','刘晨','女',19,'CS');

insert into student values('201215123','王敏','女',18,'MA');

insert into student values('201215125','张立','男',19,'IS');

insert into student values('201215126','李一平','男',18,'IS');

insert into student values('201215127','张琴','女',19,'CS');

insert into student values('201215128','王方','女',20,'MA');

insert into student values('201215129','黄林林','男',21,'IS');

CREATE TABLE  Course

         (Cno   CHAR(4) PRIMARY KEY,

         Cname  CHAR(40),    

      Cpno     CHAR(4),

    Ccredit  SMALLINT,

          );

insert into course values('1','数据库','5',4);

insert into course values('2','数学',null,2);

insert into course values('3','信息系统','1',4);

insert into course values('4','操作系统','6',3);

insert into course values('5','数据结构','7',4);

insert into course values('6','数据处理',null,2);

insert into course values('7','C语言','6',4);

CREATE TABLE  SC

         (Sno  CHAR(9),

         Cno  CHAR(4),  

          Grade  SMALLINT,

           PRIMARY KEY (Sno,Cno))

insert into sc values('201215121','1',92);

insert into sc values('201215121','2',85);

insert into sc values('201215121','3',88);

insert into sc values('201215121','4',98);