I think I understand what you're trying to do. Instead of creating a query in your database create a VIEW instead. These show up in the DataAssist Wizard along with Tables, queries do not.
Hope that helps
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.