Show the name and city of all airports.
select name, city from airports
Show the number of flight routes for each of them as a source airport.
select t1.name, t1.city, count(*) from airports as t1 join routes as t2 on t1.apid = t2.src_apid group by t2.src_apid
which of them has the most routes?
select t1.name, t1.city from airports as t1 join routes as t2 on t1.apid = t2.src_apid group by t2.src_apid order by count(*) desc limit 1