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Chapter 7. Working with Relationships > Creating Cross-Product Relationships

Creating Cross-Product Relationships

In working with non-equijoin relationship matches, you may have noticed one oddball operator in the little menu of match criteria. Most of them are familiar comparison operators—but what about the last one, the one that looks like an X?

That operator is known as a cross product (or Cartesian product if you really want to show off). The cross product does one and only one thing: It provides a “universal match” between the records in two tables. What this means is that it does no limiting of any kind. If you think of a relationship again as a kind of query, a cross-product relationship is a “find all” query. If you define a cross-product relationship from Customer to Invoice, a portal based on that relationship would always show all invoices, no matter which customer record was being viewed. The choice of fields on the left and right sides is more or less unimportant; this “all to all” relationship is fulfilled regardless of the choice of match fields.



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