If all the databases are on the same server, you can create a query that uses 3-part naming to pull data from all the databases. That is to say, if you have database A and database B on the same server, you can query database B from database A like so:
SELECT col1, col2, col3 FROM [B].[dbo].[YourTableInDatabaseB]
If they are on different servers, you can again do something similar using 4-part naming, but you would need to set up linked servers.