修改课程附件问题

app/models/mailer.rb

@@ -121,7 +121,7 @@ class Mailer < ActionMailer::Base
       count = count - 1
       for i in 0..count do
         bids =  courses[i].homework_commons.where("homework_commons.created_at between '#{date_from}' and '#{date_to}'").order("homework_commons.created_at desc")
-        attachments = courses[i].attachments.where("attachments.created_on between '#{date_from}' and '#{date_to}'").order("attachments.created_on DESC' ")
+        attachments = courses[i].attachments.where("attachments.created_on between '#{date_from}' and '#{date_to}'")
         @bids += bids if bids.count > 0
         @attachments += attachments if attachments.count > 0
       end