Query 2 table in different databases

Is there any query code that will allow joining tables that are in different databases running on the same server? If yes, how is the connection to each handled?

You need to use a 3-part name to reference the table from one database to another. The 3-part name consists of <database>.<schema>.<object>. The connection is only to the server and you can access any database to which you have permissions. You can either switch database context using USE <database> statement or use the 3-part name to reference objects.