title: How do I just fetch the primary key(s) alone from a table
body: <p>I have an entity public class GroupUser { Group g; User u; }. How do I fetch just the primary key(s) of all users. (i.e. List of u.getId() for a query where you fetch all users which belong to a group). I don't want to fetch the entire row, since it seems to take more time right now</p>