drop table course;
drop table teacher;
create table teacher (
  firstname varchar(30) not null,
  lastname varchar(30) not null,
  rank varchar(30),
  primary key (firstname,lastname)
);
create table course (
  cprefix char(4),
  cno int(4),
  title varchar(50),
  days char(5),
  starttime int(4),
  crn int(5) not null,
  tfname varchar(30),
  tlname varchar(30),
  primary key (crn),
  foreign key (tfname,tlname) references teacher(firstname,lastname) 
);
