CREATE TABLE captain (rank VARCHAR2, CLASS VARCHAR2)

Find the captain rank that has some captains in both Cutter and Armed schooner classes.
SELECT rank FROM captain WHERE CLASS = 'Cutter' INTERSECT SELECT rank FROM captain WHERE CLASS = 'Armed schooner'
SELECT "rank" FROM "captain" WHERE "CLASS" = 'Cutter' INTERSECT SELECT "rank" FROM "captain" WHERE "CLASS" = 'Armed schooner'