search for: client_slot_count

I am not sure that this is entirely a rails question as I am trying to run the command in postgres and I am getting the same error... controller code... @client_slot_count = ClientSlotsDaily.find(:all, :conditions => ["created_at > ? AND created_at < ? AND facility_id = ? AND client_id IS NOT NULL", starting_date, ending_date, @facility.id], :group => ''client_id'') error reported is... PGError...