DB

create table department (
        dept_name varchar (20) not null,
        building varchar (25) not null,
        budget numeric (8,0) not null,
        primary key(dept_name));

create table instructor (
        ID char (10)not null,
        dept_name varchar(20) not null,
        name varchar(20) not null,
        salary numeric (8,0) not null,
        primary key(ID),
        foreign key (dept_name) references department);

create table student (
        ID varchar (10),
        name varchar(20) not null,
        dept_name varchar(20),
        tot_cred numeric(3,0),
        primary key(ID),
        foreign key (dept_name) references department);

create table course (
        course_id varchar (10) not null,
        title  varchar(20) not null,
        dept_name varchar(20) not null,
        credits numeric(2,0),
        primary key(course_id),
        foreign key (dept_name) references department);

create table prereq (
        course_id varchar (10) not null,
        prereq_id varchar(20) not null,
        primary key(course_id,prereq_id),
        foreign key (course_id) references course);

 create table time_slot (
        time_slot_id varchar (20) not null,
        day varchar(20) not null,
        start_time varchar(20) not null,
        end_time varchar(20),
        primary key(time_slot_id,day,start_time),
        foreign key (time_slot_id,day,start_time ) references time_slot);

  create table time_slot (
        time_slot_id varchar (20) not null,
        day varchar(20) not null,
        start_time varchar(20) not null,
        end_time varchar(20),
        primary key(time_slot_id,day,start_time),
        foreign key (time_slot_id,day,start_time ) references time_slot);