确定分组后如何选择记录。 （Rails 3.0）

Question

I have been using a scope that allows for the retrieval of the record with the highest id in a given group. I recently changed the way records are added to the database so that the record with the highest id is not necessarily the record with the most recent data; that would be the record with the highest :end_time.

scope :latest_record_in_group, unique.select('max(id) as id')

where unique is as follows:

scope :unique, group(:field_1, :field_2, :field_3, :field_4)

Now what I need is to select the id of the record with the highest :end_time and I'm baffled. It seems that I can't alter how activeRecord decides which of the records in a group gets selected as the representative of said group. As it stands, it seems to be the record with the highest :id by default. Any insight as to how I can select the record with the highest :end_time would be greatly appreciated.

EDIT: disambiguation

Answer 1

If I understand your question you should use

case you're using rails 3

Model.find(:all, :order => "end_time")

case you're using rails4

Model.order(:end_time).all