select 
  `e`.`last_name`,`e`.`first_name`,`depa`.`dept_name`
from

  (
      `employees` as `e` 
    left join 
      `dept_emp` as `de`
    on
      `e`.`emp_no`=`de`.`emp_no`
  )
left join
    `departments` as `depa`
on
   `depa`.`dept_no`=`de`.`dept_no`