create database Class

create table class (
    ClassId int primary key identity(1,1) not null ,
   ClassName nvarchar(50) not null,);

create table student (
     ClassId int primary key identity(1,1) not null ,
   ClassName nvarchar(50) not null,
   StudentSex  nvarchar(50) not null default '3',
   StudentBirth date,
   StudentAddress nvarchar(255) not null default ' ',
   ClassId2 int not null,);

create table Course (
CourseId int primary key identity(1,1) not null ,
CourseName nvarchar(50) not null ,
CourseCredit tinyint not null default '0',)

create table ClassCourse (
ClassCourseId int primary key identity(1,1) not null ,
ClassId int not null,
CourseId int not null,)

create table Score (
ScoreId int primary key identity(1,1) not null ,
StudentId int not null,
CourseId int not null,
Score int not null,)

 alter table Student add StudentIdentityCard  varchar(20) not null default ' ';

 alter table Score add IsResit tinyint  not null default '0 ';