SQLEditor 2.9

SQLEditor is a SQL database design and entity relationship diagram (ERD) tool for OS X. It replaces typing SQL by hand with dragging, dropping, and clicking, making database creation faster and easier.

And if you already have a database, then SQLEditor can help you see what it looks like by reverse engineering a diagram.
SQLEditor supports exporting database designs to MySQL, Postgres, Oracle, and others. Plus it also imports and exports Ruby On Rails Migration files.
Site license: $349, Single Copy $79. Discounts for qualified educational orders.
Buy now and receive a free upgrade to SQLEditor 3 when released