CREATE TABLE station (station_id NUMBER, name CLOB, annual_entry_exit NUMBER, annual_interchanges NUMBER, total_passengers NUMBER, location CLOB, main_services CLOB, number_of_platforms NUMBER)
CREATE TABLE train_station (train_id NUMBER, station_id NUMBER)
CREATE TABLE train (train_id NUMBER, name CLOB, time CLOB, service CLOB)

Show all locations which don't have a train station with at least 15 platforms.
SELECT location FROM station EXCEPT SELECT location FROM station WHERE number_of_platforms >= 15
SELECT "location" FROM "station" EXCEPT SELECT "location" FROM "station" WHERE "number_of_platforms" >= 15