I recently discovered schemaspy and while it took a bit of working knowledge of java (need to execute a jar file from the command line) to get it working, it’s absolutely fantastic and one of the most sophisticated tools for dealing with ERDs at the DB level. Plus it’s open source! The only things I see that are possible improvements with this product are the fact that you don’t need to bootstrap a local database to generate this and it’s probably faster and easier to generate. I had a reasonably complex schema (200 ish tables with relationships) and schemaspy took about 3 minutes to generate the output. Once you do generate it though, it’s just a bunch of html and SVG in a folder so you don’t have to regenerate it until your scheme is updated.