How many airlines do you have?
select count ( * ) from airlines
How many routes does each airline have?
select t1.name, count ( * ) from airlines as t1 join routes as t2 on t1.alid = t2.alid group by t2.alid
What are the names of the top 10 airlines with the most number of routes?
select t1.name from airlines as t1 join routes as t2 on t1.alid = t2.alid group by t2.alid order by count ( * ) desc limit 10