–For each country, determine battles in which the ships of the given country did not participate.
–Result set: country, battle
selecty.country, name from
(select distinct country from Classes) y
(select name from Battles) z
wherename not in
(select battle from (select battle, country from Classes c inner join ships s on s.class = c.class inner join Outcomes o on s.name = o.ship union select battle, country from Classes c inner join Outcomes o on o.ship = c.class) u where u.country = y.country )