select emp_no,
    first_name,
    last_name,
    btype,
    salary,
    case when btype=1 then round(salary*0.1,1)
         when btype=2 then round(salary*0.2,1)
         else salary*0.3
    end as bonus
from employees
left join emp_bonus using(emp_no)
right join salaries using(emp_no)
where btype is not null and to_date='9999-01-01'
order by emp_no