Do you look for a solution in OBIEE or in general in your DB?
OBIEE can definitely manage your 7 tables and query them all together (defining 7 LTS for your logical table) or you can just "unify" them at the DB level. The simplest way is a view.
I would avoid an opaque view in OBIEE as that's really hiding logic.
I would avoid doing it with a VIEW in the DB but rater importing all 7 and use OBIEE's fragmentation if there is a way of telling to OBIEE which partition of data is within each table.
The view option will always query all 7 sources while using fragmentation you'll hit only the fragment with the data you need if you specify the fragment partitioning key