CREATE TABLE stock (shop_id NUMBER, device_id NUMBER, quantity NUMBER)
CREATE TABLE device (device_id NUMBER, device CLOB, carrier CLOB, package_version CLOB, applications CLOB, software_platform CLOB)
CREATE TABLE shop (shop_id NUMBER, shop_name CLOB, location CLOB, open_date CLOB, open_year NUMBER)

How many different software platforms are there for devices?
SELECT COUNT(DISTINCT software_platform) FROM device
SELECT COUNT(DISTINCT "software_platform") FROM "device"