GNU Ferret (formerly known as GerWin) is a free entity relationship and reverse engineering tool. It aids you in creating data models and implementing them in a relational database. You can draw your data model via an entity-relation diagram, generate the tables from it (another graphical diagram), and then generate the SQL that creates such relational tables. Several SQL dialects are supported (for most popular free software database systems) and it is very easy to patch the sources to support more.
