The discounts table contains discounts in stores.
discounts is defined as:
create table discounts (discounttype varchar(40) not null, stor_id char(4) null, lowqty smallint null, highqty smallint null, discount float not null)
Its primary keys are discounttype and stor_id:
sp_primarykey discounts, discounttype, stor_id
Its stor_id is a foreign key to stores:
sp_foreignkey discounts, stores, stor_id