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

For each country, what is the average elevation of that country's airports?
SELECT AVG(elevation), country FROM airports GROUP BY country
SELECT AVG("elevation"), "country" FROM "airports" GROUP BY "country"