CREATE TABLE routes (src_apid VARCHAR2)
CREATE TABLE airports (name VARCHAR2, apid VARCHAR2, country VARCHAR2)

Find the busiest source airport that runs most number of routes in China.
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
SELECT "T1"."name" FROM "airports" "T1" JOIN "routes" "T2" ON "T1"."apid" = "T2"."src_apid" WHERE "T1"."country" = 'China' GROUP BY "T1"."name" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY