Scientific databases and web databases maintain large and heterogeneous data. The databases contain over hundreds or even thousands of relations and attributes. Predefined old query forms are not able to satisfy various ad-hoc queries from users on those databases. Dynamic query form, a new database query form interface used to dynamically generate query forms. The use of DQF is to capture a user's preference and rank query form components, assisting user to make decisions. The query form is an iterative process and is guided by the user.