gistfile1.rb

class Post < ActiveRecord::Base

  scope :date_counts, lambda {
    group('DATE_FORMAT(created_at, "%Y/%m")').count
  }
  ##Post.date_counts GENERATES ERROR: ArgumentError: Unknown key(s): 2009/01, 2009/02, 2009/03, 2009/04, 2009/06 ... etc

  def self.date_counts
    self.group('DATE_FORMAT(created_at, "%Y/%m")').count
  end
  ##Post.date_counts works as expected


end