Is it possible to model tables belonging to different databases in the same schema?

Question

I need to build a system that in order to deliver the desired results to the user, queries (it uses a join operation) two tables each of them belonging to a different database. Therefore between them there is no physical relationship.

However, conceptually, there is a one-to-many relationship between them and I need to show this relationship in a ER model.

The modelling is an easy task, although I am not sure whether it is an approved practice to create a relationship between two tables which are not physically connected. If that is the case "permitted" is there any graphical ER convention to specify that the tables belong to different databases and that the relationship is just conceptual?

PS: the model I would like to design is used for both system documentation and to show the system structure to its stakeholders

Answer 1

Yes, its possible to model.

And apparently in many RDBMS it is not possible to implement without some (sometimes significant) drawbacks.