Groupwise max then join

Question

I have a votes table that has many subitems. I have a subitems action table that records what action was performed by which user on which group, on which subitem, on which vote

Users can either cast/uncast/delete/update create on actions.

To find out if a user 'belongs' to a subitem, I used groupwise max.The logic is that among all the cast or uncast actions that has has performed on a subitem, if the latest timestamp is cast, then he has indeed voted on it. If it is uncast then he has not.

This is what the query looks like :

select  act.user_id,act.anonymous
    from  
      ( SELECT  sub_item_id,user_id ,max(created_at) as newestAction
            from  vote_sub_item_action
            where  sub_item_id =10
              AND  user_id=910
              AND  action_type IN('ACTION_CAST_VOTE','action_uncast_vote')
            GROUP BY  user_id 
      ) as x
    inner join  vote_sub_item_action as act on act.user_id = x.user_id
      and  act.created_at = newestAction
      and  act.action_type='action_cast_vote'
      and  act.sub_item_id =x.sub_item_id; 

Now I would like to get all the subitems that 'belong' to him from a particular vote. The logic of belongs is the same as above.

How may I do that?