1 #example
       2 class AddCategoryIdToPosts < ActiveRecord::Migration
       3   def self.up
       4     change_table :posts do |t|
       5       t.references :category
       6     end
       7   end
       8 
       9   def self.down
      10     change_table :posts do |t|
      11       t.remove_references :category
      12     end
      13   end
      14 end
      

 1 # another exmample. note remove_integer doesn't work. just use plain old 'remove'
       2 class AddRedirectLocaleToPages < ActiveRecord::Migration
       3   def self.up
       4     change_table :pages do |t|
       5       t.integer :redirect_locale, :default => 0
       6     end
       7   end
       8 
       9   def self.down
      10     change_table :pages do |t|
      11       t.remove :redirect_locale, :default => 0
      12     end
      13   end
      14 end