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

What are the carriers of devices that are not in stock anywhere?
SELECT carrier FROM device WHERE NOT device_id IN (SELECT device_id FROM stock)
SELECT "carrier" FROM "device" WHERE NOT "device_id" IN (SELECT "device_id" FROM "stock")