Disadvantage of wpf on database

No disadvantages, by one simple reason: WPF has nothing to do with databases. In .NET, people almost always work with ADO.NET. One can use ADO.NET with or without WFP, and WPF with or without ADO.NET.

Not only the question makes no sense, but your thinking is dangerous for you as a developer. It means that you hardly understand one basic principle: separation of concerns.

Please see:

http://en.wikipedia.org/wiki/Separation_of_concerns[^];

http://en.wikipedia.org/wiki/ADO.NET[^],
http://msdn.microsoft.com/en-us/library/aa286484.aspx[^];

http://en.wikipedia.org/wiki/Windows_Presentation_Foundation[^];
http://msdn.microsoft.com/en-us/library/ms754130.aspx[^].

Also, the UI is a very special aspect of code. Is should be separated as well as possible. To get an idea of existing approaches, I would advise to learn the following architectural patterns (http://en.wikipedia.org/wiki/Architectural_pattern_(computer_science)[^]):

MVVM — Model View View Model,
http://en.wikipedia.org/wiki/Model_View_ViewModel[^],

MVC — Model-View-Controller,
http://en.wikipedia.org/wiki/Model-view-controller[^]),

MVA — Model-View-Adapter,
http://en.wikipedia.org/wiki/Model–view–adapter[^],

MVP — Model-View-Presenter,
http://en.wikipedia.org/wiki/Model-view-presenter[^].

—SA