This paper describes ProSQL, a novel prototyping tool to support the development of extensions to SQL. ProSQL provides a simple way to prototype the features of a proposed extension and thus provide a proof of concept. Further, it provides proposers and reviewers of extensions with a clearer view of their positive and negative features. The approach adopted has been to build a wrapper around an existing database management system, in this case Microsoft Access, and to provide a collection of interfaces with which a designer can define extensions to the basic relational database.