sum enumeration with LIMIT

rubyonrails-talk
1

Hi everyone.

I'm trying to SUM the places of the first 5 finishers in a Cross Country running event. In a Cross Country race the team score is based upon the sum of the top 5 runners on your team. The lowest team score at the competition wins.

I have EVENTS(the race), PARTICIPANTS(the runner), and EVENT_PARTICIPANTS(a runner in a race).

Within event_participant I have this code, which doesn't work as it adds places beyond the 5th runner.

  def self.score_5     self.calculate(:sum, :finish_place, :order => :finish_place, :limit => 5)   end

It appears that the LIMIT is ignored or is applied after the summation.

Any suggestions?

2

Hi everyone.

I'm trying to SUM the places of the first 5 finishers in a Cross Country running event. In a Cross Country race the team score is based upon the sum of the top 5 runners on your team. The lowest team score at the competition wins.

I have EVENTS(the race), PARTICIPANTS(the runner), and EVENT_PARTICIPANTS(a runner in a race).

Within event_participant I have this code, which doesn't work as it adds places beyond the 5th runner.

def self.score_5    self.calculate(:sum, :finish_place, :order => :finish_place, :limit => 5) end

It appears that the LIMIT is ignored or is applied after the summation.

It's applied after (so if you did select sum(foo) from bars limit 5
then you'd only get 5 rows back). Something like SELECT sum(finish_place) from   (SELECT * from some_table order by finish_place limit 5) as sub_select

should do it.

Fred

3

Are us suggesting find_by_sql?

4

I'd like to know if there is a way to use ActiveRecord to do this.

Thx