This must be a "DBMS 101" classic, but I don't seem to be able to figure it out:

I have a discount table that has a primary key, a foreign key to customer and a foreign key to the items table. I.e. "some customers have discounts on some items".

I have an order header table that contains a foreign key to the customer and order detail that has a foreign key to the item.

I'm trying to build a dbms query or queries (in msaccess) that would join the discount table to the de-normalized order table (I .e. a join of the order header and the order detail on the header key).