Here is a tool that generates relational diagrams from MySQL (on Windows at the moment). I have used it on a database with 400 tables. If the diagram is too big for a single diagram, it gets broken down into smaller ones. So you will probably end up with multiple diagrams and you can navigate between them by right clicking. It is all explained in the link below. The tool is free (as in free beer), the author uses it himself on consulting assignments, and lets other people use it. http://www.scmlite.com/Quick%20overview