Two back-ends, how define relationships?

[Guest]

I have to maintain an application that I did not write and is set up in a
weird way.
There are two back-ends, one is protected by a password and contains a
mini-application to update referenece tables. There are no relationships
defined but there really needs to be as there are several important
one-to-many relationships. The problem is the 'many' side is in one database
and the 'one' side in the other database. Can relationships be defined in
these circumstances?

 

[John Spencer]

Yes and mostly NO.

Yes: You can set up a relationship that will be used when you open a query
to set default relationship.

No: HOWEVER, to have a relationship that controls the data - enforce
referential integrity, cascade delete, cascade update - the tables must be
in the same database AND the relationships must be set up in the database
containing the tables.