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

What are the carriers of devices that are in stock in more than a single shop?
SELECT T2.carrier FROM stock AS T1 JOIN device AS T2 ON T1.device_id = T2.device_id GROUP BY T1.device_id HAVING COUNT(*) > 1
SELECT "T2"."carrier" FROM "stock" AS "T1" JOIN "device" AS "T2" ON "T1"."device_id" = "T2"."device_id" GROUP BY "T1"."device_id" HAVING COUNT(*) > 1