Crystal Reports must first connect to the database before it can process any data. Therefore, you cannot use a parameter to control which database CR uses. However, you could create a view, or multiple views in one database which, using linked servers or db links, return data from other databases. Then, by using a command object (database->database expert ->connection->add command) you could have a parameter to control how you select from the view, or even which view is used. If you can have a column in the view to indicate where the data originated, then the parameter can control the result set.