What are the names of ships that are commanded by both captains with the rank of Midshipman and captains with the rank of Lieutenant?
select t1.name from ship as t1 join captain as t2 on t1.ship_id = t2.ship_id where t2.rank = 'Midshipman' intersect select t1.name from ship as t1 join captain as t2 on t1.ship_id = t2.ship_id where t2.rank = 'Lieutenant'