I have a set of categories and would like to retrieve all entities of a specific type (it's a custom entity type but unless I'm mistaken the query system doesn't care as long as I have mappings for it etc).

I can easily use the querysystem to retrieve all entities in one specific category but I can't figure out how to retrieve all entities that are in atleast one of a set of categories, or (what I really want to do) not in the same set.

Any help would be appreciated!