Architectural question

Hello everybody.

I would like to create a database. It's a structure of about 20
items (tables, views, etc.)

Then I would like to make it a template, because I need 7 copies
of this structure, possibly a growing number.

The only problem is that there are four tables in it, which are
general, so it would be the finest to make them common. For
example in a database "commondb".

But I don't know if I could somehow create a construction like this:
SELECT * from sometable
WHERE somecolumn IN (SELECT * FROM <the-common-db>::atable)

Since now I used Delphi, and I could reference databases as
directories in my file system, so it wasn't a problem.

Any ideas to solve this?

Thanks in advance,
Baldvin