CREATE TABLE ship (ship_id NUMBER, name CLOB, type CLOB, built_year NUMBER, class CLOB, flag CLOB)
CREATE TABLE captain (captain_id NUMBER, name CLOB, ship_id NUMBER, age CLOB, class CLOB, rank CLOB)

Find the captain rank that has no captain in Third-rate ship of the line class.
SELECT rank FROM captain EXCEPT SELECT rank FROM captain WHERE class = 'Third-rate ship of the line'
SELECT "rank" FROM "captain" EXCEPT SELECT "rank" FROM "captain" WHERE "class" = 'Third-rate ship of the line'