Show me the names of all the pilots.
select distinct pilot from flight
Which of these pilots piloted a flight in the United States?
select distinct t2.pilot from airport as t1 join flight as t2 on t1.id = t2.airport_id where t1.country = "United States"
What about the pilots who did it at 'Billund Airport'?
select distinct t2.pilot from airport as t1 join flight as t2 on t1.id = t2.airport_id where t1.name = "Billund Airport"
Which pilots did either one of those?
select distinct t2.pilot from airport as t1 join flight as t2 on t1.id = t2.airport_id where t1.country = 'United States' or t1.name = 'Billund Airport'