CREATE TABLE track (track_id NUMBER, name CLOB, location CLOB, seating NUMBER, year_opened NUMBER)
CREATE TABLE race (race_id NUMBER, name CLOB, class CLOB, date CLOB, track_id CLOB)

What are the classes of races that have two or more corresponding races?
SELECT class FROM race GROUP BY class HAVING COUNT(*) >= 2
SELECT "class" FROM "race" GROUP BY "class" HAVING COUNT(*) >= 2