CREATE TABLE airlines (alid DECIMAL, name TEXT, iata TEXT, icao TEXT, callsign TEXT, country TEXT, active TEXT)
CREATE TABLE routes (rid DECIMAL, dst_apid DECIMAL, dst_ap TEXT, src_apid DECIMAL, src_ap TEXT, alid DECIMAL, airline TEXT, codeshare TEXT)
CREATE TABLE airports (apid DECIMAL, name TEXT, city TEXT, country TEXT, x DECIMAL, y DECIMAL, elevation DECIMAL, iata TEXT, icao TEXT)

How many routes go from the United States to Canada?
SELECT COUNT(*) FROM routes WHERE dst_apid IN (SELECT apid FROM airports WHERE country = 'Canada') AND src_apid IN (SELECT apid FROM airports WHERE country = 'United States')
SELECT COUNT(*) FROM "routes" WHERE "dst_apid" IN (SELECT "apid" FROM "airports" WHERE "country" = 'Canada') AND "src_apid" IN (SELECT "apid" FROM "airports" WHERE "country" = 'United States')