Is there a good SQL Diagram Editor/Drawing Mac App Tool?

MySQL Workbench is good enough for most programming demands. You can create EER Model and can also synchronize the model with DB Changes or vice versa. You can use it with no cost as it's a open-source application. I have been using MySQL for a year and it is very useful for me. I recommend it to you if you don't need any enterprise features and performance.

The only Mac only tool I know (and I would love to hear of others here) is SQLEditor. Unfortunately, there doesn't appear to be any support for Stored Procedures or other objects beyond tables and views.

There are also cross-platform solutions (mostly Java-based). In a recent search I evaluated DBWrench and DBVisualizer. When all was said and done, I decided to stay with a Windows solution running under Parallels.

MySQL Workbench is great, though I found that in a lot of cases OmniGraffle works wonderful, especially if you're not so much into "doing it painfully correct according to theory learnt at university" but rather getting the job done.

You might want to check out the Navicat line of products. I use Navicat Premium and it's a really great all-in-one tool for many DBs, including MySQL, Postgres, SQLITE, Oracle, and MS SQL Server. It includes a Model tab where you can view and edit existing DBs or create de novo ones, sketch everything out, define relationships, export SQL, have access to an auto-layout function, and all sorts of other goodies.

There are several versions stepping up to the Premium product, including a separate Data Modeler program, so you'll have to browse around to see what fits your needs. It will set you back a little bit of cash, depending on the version, but you can download a 30-day free trial to make sure it's what you need.

I hope this helps!