Find the busiest source airport that runs most number of routes in China.
create table routes (src_apid varchar, PRIMARY KEY (src_apid)); create table airports (name varchar, apid varchar, country varchar, PRIMARY KEY (name))
select t1.name from airports as t1 join routes as t2 on t1.apid = t2.src_apid where t1.country = 'china' group by t1.name order by count(*) desc limit 1