删除了courses表中的school列。

重新设计下表= =

db/migrate/20140319092720_remove_school_from_courses.rb

@@ -0,0 +1,9 @@
+class RemoveSchoolFromCourses < ActiveRecord::Migration
+  def up
+    remove_column :courses, :school
+  end
+
+  def down
+    add_column :courses, :school, :string
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20140318021747) do
+ActiveRecord::Schema.define(:version => 20140319092720) do
 
   create_table "activities", :force => true do |t|
     t.integer "act_id",   :null => false
@@ -173,7 +173,6 @@ ActiveRecord::Schema.define(:version => 20140318021747) do
     t.string   "setup_time"
     t.string   "endup_time"
     t.string   "class_period"
-    t.string   "school"
   end
 
   create_table "custom_fields", :force => true do |t|
@@ -601,7 +600,6 @@ ActiveRecord::Schema.define(:version => 20140318021747) do
   create_table "schools", :force => true do |t|
     t.string "name"
     t.string "province"
-    t.string "city"
   end
 
   create_table "seems_rateable_cached_ratings", :force => true do |t|