Martin, others,

Since version 8.1 you can use multiple databases on the same server and from the same manufacturer. There are a couple of issues to watch out for. Issues like comparing but in most cases this is not an issue.

You cannot combine different databases (like MSSQL and PostGreSQL or RDS) in one report.

You can - and one of the sample reports show this - have the main report using a different data-source than a sub-report.