I showed before how simple it is to create a dependent or cascading LOV using ADF BC.
This will allow you to filter one list based on the selection in another list.
However, if you'll try to get this to work inside an af:query component - it won't work out of the box.
Luckily Steve Muench pointed me to a small setting that will get it to work in an af:query component.
Basically all you need to do is set the autosubmit property of the attribute in the viewObject.
Here is a short demo showing you how to do this. (it starts where the previous video ends).