sql answers.txt

1.
select a.* from employee a, employee b
where  b.id = a.chief_id
and    a.salary > b.salary;

2.
select a.* from employee a
where  a.salary = (select max(salary) from employee b
                    where  b.department_id = a.department_id);

3.
select department_id from employee 
group  by department_id 
having count(*) <= 3;

4.
select a.* from employee a
left   join employee b on (b.id = a.chief_id and b.department_id = a.department_id)
where  b.id is null;

5.
with sum_salary as 
	(select department_id, sum(salary) salary from   employee group  by department_id)
select department_id from   sum_salary a       
where  a.salary = (select max(salary) from sum_salary);