Sorting with Associations ??

With ActiveRecord, how do I sort results using associations?

For example, I have

class Roster < ActiveRecord
  # name => text
  has_many :members
end
class Member < ActiveRecord
  # zip_code => integer
  belongs_to :roster
end

I would like to generate a list of members, grouped by roster name,
sub-sorted by zip code.

Something like this: Member.order("roster.name, zip_code").all

But I can't get the syntax quite right - I've played around with join
and include - can anyone tell me the right syntax to use??

thanks, Andy

Remember that table names are plural.

Member.joins(:roster).order("rosters.name, zip_code")

That did it ! Thank you very much !!!!!