CREATE TABLE country (country_id NUMBER, name CLOB, population NUMBER, area NUMBER, languages CLOB)
CREATE TABLE roller_coaster (roller_coaster_id NUMBER, name CLOB, park CLOB, country_id NUMBER, length NUMBER, height NUMBER, speed CLOB, opened CLOB, status CLOB)

What is the average speed of roller coasters?
SELECT AVG(speed) FROM roller_coaster
SELECT AVG("speed") FROM "roller_coaster"