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')
[{'count(*)': 364}]