CREATE TABLE shop (Shop_Name VARCHAR, Shop_ID VARCHAR)
CREATE TABLE stock (Shop_ID VARCHAR)

Show names of shops that have more than one kind of device in stock.
SELECT T2.Shop_Name FROM stock AS T1 JOIN shop AS T2 ON T1.Shop_ID = T2.Shop_ID GROUP BY T1.Shop_ID HAVING COUNT(*) > 1
SELECT "T2"."Shop_Name" FROM "stock" AS "T1" JOIN "shop" AS "T2" ON "T1"."Shop_ID" = "T2"."Shop_ID" GROUP BY "T1"."Shop_ID" HAVING COUNT(*) > 1