JavaScript Boolean Search Query Builder Interface Library?

Question

Are there any (good/usable/not ugly) JavaScript/interface libraries for managing the creation of custom boolean style queries, similar to the Google Analytics Advanced Segment interface?

Basically, a dynamic interface for query building that can be used to connect to a custom query builder on the backend (in my case, MySQL, but it needn't be database specific).

I've searched around, and haven't found anything helpful or usable.

Answer 1

http://redquerybuilder.appspot.com/ is not pretty but aiming to be usable by non-techy people.

I should make it clear that I'm one of the authors of this project.