Consider the following database schema that describes information about products that are supplied by stores. The relational schema Store has as primary key the attribute storeid and the relational schema Product has as primary key the attribute pid. The relational schema Supply stores pairs of stores and products supplied by the former; the primary key is the combination of storeid and pid; moreover, storeid is a foreign key to Store and pid is a foreign key to Product.

Store $($storeid$,$ sname, employee$\_$number, city$)$ Product $($pid$,$ pname, price$)$

Supply $($storeid$,$ pid$)$