one-to-many-or-none table relationship? (minimum cardinality)

[racecar333]

I have two tables - one for what's in stock (parent), and one for what has been ordered (child).



I am trying to set up a relationship between the SKU numbers of each table, the primary key being the SKU number field of the stockitems table (being the foreign key of the orderitems table).

Every time I do this, it is a one-to-many relationship, but it does not work because there are some entries that are in the stockitems table and NOT in the orderitems table.

So, how do I define a minimum cardinality for the "many" side of this relationship? (so that it would be one-to-many-or-none)

[racecar333]

[orange]

Please show table structures. How about a description of what you are trying to do in business terms?