A simple way of handling custom sql queries without involving ActiveRecord. (Using postgresql)

context.rb

# encoding: utf-8

class Context

  class Context::Result

    def initialize(*args, &block)
      args.extract_options!.each do |attr, value|
        send("#{attr}=", numeric?(value)) if respond_to?("#{attr}=")
      end
      block.call(self) if block
    end

    protected
    def numeric?(value)
      if value.is_a?(String) && value =~ /^\d*$/
        value.to_i
      else
        value
      end
    end
  end

  protected
  def select_all(sql)
    con.select_all compress(sql)
  end

  def compress(sql)
    sql.squeeze(' ').gsub(/\n/,'').strip
  end

  def con
    ActiveRecord::Base.connection
  end

end

statistics_order.rb

# encoding: utf-8

class StatisticsOrder

  class Result < Context::Result
    attr_accessor :name, :order, :delivered, :paid
  end

  def each(&block)
    items.each(&block)
  end

  protected
  def items
    @items ||= select_all(sql).map do |hash|
      Result.new hash
    end
  end

  private
  def sql
    <<-sql
      SELECT "sales"."name", COUNT(*),
              SUM(CASE "orders"."delivered_at" IS NOT NULL THEN 1 ELSE 0 END) as "delivered",
              SUM(CASE "orders"."paid_at" IS NOT NULL THEN 1 ELSE 0 END) AS "paid"
      FROM "orders"
        JOIN "sales" ON "orders"."sales_id" = "sales"."id"
      WHERE "sales"."created_at" > "2014-01-13 12:54:00"
      GROUP BY "sales"."name"
    sql
  end
end