#206 エラー修正

backend/app/controllers/posts_controller.rb

@@ -71,7 +71,7 @@ class PostsController < ApplicationController
           'posts.original_created_from,' +
           'posts.created_at) '
         when 'updated_at'
-          'posts.updated_at_all'
+          updated_at_all_sql
         else
           "posts.#{ order[0] }"
         end