select e.emp_no,first_name,last_name,btype,salary,
    (case btype
    when 1 then salary*0.1
    when 2 then salary*0.2
    else salary * 0.3 end) as bonus
from employees e inner join emp_bonus b on e.emp_no =b.emp_no
    inner join salaries s on e.emp_no = s.emp_no 
where s.to_date = '9999-01-01'