So far, only Relation objects created between two permanent tables that exist in the same database have been discussed. With Microsoft Jet, you can create relationships between tables and QueryDef objects, or between tables in a local database and tables in external databases.
It’s not possible to create a cascading update or cascading delete relationship between a table and a QueryDef object. Nor is it possible to enforce referential integrity between a table and a query. Enforced referential integrity is valid only for relationships between tables. Creating a relationship between a table and a query has no effect on the structure of your database.
The primary benefit of creating a relationship between a table and a query or between a local table and a linked table is for documentation purposes and for interactive use with a product such as Microsoft Access. Microsoft Access can make certain assumptions about the relationships between your tables if you have defined these non-enforceable relationships. For example, if you create a relationship between a table and a query, and then add that table and query to a new query in query Design view, Microsoft Access automatically draws in the join line between the table and the query.