The problem is that I only get the users with a statistics record and
I also want users without any stastics. I think the problem is caused
by :conditions => ["statistics.event_id = ?", event.id] but I don't
know how to include the event_id in another way.
Someone can help me out?
Try using the :joins parameter and manually join to the statistics table
with an OUTER join, or use the find_by_sql method if you have to.
The joins param value will be something like :joins => "left outer join
statistics s on s.user_id = user.id"
Having the left outer join should still allow you to filter the the
statistics with the event_id and include the users with and without