Question: Show names of shops that have more than one kind of device in stock.
Schema: create table shop (shop_name varchar, shop_id varchar, PRIMARY KEY (shop_name)); create table stock (shop_id varchar, PRIMARY KEY (shop_id))
SQL: 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