I really enjoy database design and the whole concept of managing data semantically and all the logic that comes with it.
My knowledge level when it comes to databases is
There is only one rigorous technique for conceptually modeling a relational database schema that I know of (and I've spent a lot of time looking). It's confusingly named "Object-Role Modeling". Here are a couple references.
http://www.agilemodeling.com/artifacts/ormDiagram.htm
http://www.tdan.com/view-articles/5033
http://en.wikipedia.org/wiki/Object_role_modeling
http://en.wikipedia.org/wiki/NORMA
and here's a plugin for Visual Studio