Do you mean something like this:
Diego - thanks for your reply. I do not think either of those addresses my need.
I need to be able to link two tables that do not have an explicit secondary key -- they are joinable through a third table. This is a common design pattern. For example,
PRODUCTS has one or more entries in ProductCategories, each of which has a Category Key. That allows one to find all the Categories for a Product and visa versa. The ProductCategores table has two columns
PRODUCT and CATEGORY. These columns contains keys that appear on rows in PRODUCTS and in the CATEGORIES, the two tables that need to be joined through the association table.