I am building a couple of websites. The idea is that the two (later to be more) sites share some info such as user accounts.
Now, I want to use a separate database for each website, but how would I manage to link the user tables?
Currently all the databases exist on the same server, so I beleive it would be possible to keep the joint data in its own database and be able to access it in database.table.column notation.
However, would I pay a performance hit doing it this way? In particular if I were performing joins across databases?
Is there another way to do it. I.e. could I create a virtual table in one database that is a linked copy one from the other database.
Also, if the database grows beyond a single server, I guess I could use replication to do this?