Return all the staff department assignments.
select * from staff_department_assignments
Count the number of assignments for each staff.
select count (*) from staff_department_assignments group by staff_id
List the names of staff who have been assigned multiple jobs.
select t1.staff_name from staff as t1 join staff_department_assignments as t2 on t1.staff_id = t2.staff_id group by t2.staff_id having count (*) > 1