--8-1
select distinct department_id from departments
minus
select distinct department_id from employees   where job_id='ST_CLERK';
--8-2
select country_id, country_name  FROM countries
minus
select l.country_id, c.country_name 
from locations l 
     Join countries   c on( l.country_id  = c.country_id)
     join departments d on( d.location_id = l.location_id);

select l.country_id, c.country_name 
from locations l, countries  c ,departments d
where ( l.country_id =c.country_id) 
  and (d.location_id=l.location_id);
  
--8-3
select distinct job_id, department_id from employees where department_id=10
union all
select distinct job_id, department_id from employees where department_id=50
union all
select distinct job_id, department_id from employees where department_id=20
order by department_id;
  
--8-4
select distinct employee_id, job_id from employees 
intersect 
select distinct employee_id, job_id from job_history;

--8-5
select last_name,     department_id, to_char(null)   from employees 
union
select to_char(null), department_id, department_name from departments;