text: create table salgrade(
    grade number,
    losal number,
    hisal number
  );
  insert into salgrade values (1, 700, 1200);
  insert into salgrade values (2, 1201, 1400);
  insert into salgrade values (3, 1401, 2000);
  insert into salgrade values (4, 2001, 3000);
  insert into salgrade values (5, 3001, 9999);
  
  