JavaScript Boolean Search Query Builder Interface Library?

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.

A fairly new one is the jQuery QueryBuilder which can be found here: http://querybuilder.js.org/

It supports the following logical and filter operators:

• and
• or
• equal / not equal
• in / not_in
• begins with / not begins with
• contains / not contains
• ends with / not ends with
• is empty / is not empty
• is null / is not null
• less / less or equal /greater / greater or equal
• between / not between

The basic output is JSON but plugins for SQL or MongoDB syntax import/export are available too.

Some demos can be found here: http://querybuilder.js.org/demo.html