What are all the department names?
select dname from department
Order them by the number of members in each.
select t1.dname from department as t1 join member_of as t2 on t1.dno = t2.dno group by t2.dno order by count(*) asc
Which has the fewest?
select t1.dname from department as t1 join member_of as t2 on t1.dno = t2.dno group by t2.dno order by count(*) asc limit 1