I use ArgoUML for database modeling, just add some stereotypes such as Database, Schema, Table, PK, FK with class diagram.
For a typical example, see these useful page:
- http://argouml-db.tigris.org/documentation/DB_UML_Guide.htm
- http://argouml-db.tigris.org/documentation/UML_Model.htm
From ahm507.blogspot.com