Show me names of all the staff members.
select staff_name from staff
List the first and last names of engineers each staff member has contacted.
select t1.staff_name, t3.first_name, t3.last_name from staff as t1 join engineer_visits as t2 on t1.staff_id = t2.contact_staff_id join maintenance_engineers as t3 on t2.engineer_id = t3.engineer_id