Learning Rails 3.0 - Migration Help - belongsTo

I'm working on a photo gallery app. Photo has a belongsTo relationship to Album (Album has_many realtionship to Photo) How do I create the migration that adds this relationship to the database correctly? I have tried - rails generate add_album_to_photo but that comes th开发者_如何学JAVArough as an empty migration. I could use a push in the right direction.

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Assuming tables albums and photos exist already, all you have to do is add a column album_id to your photos table:

class AddAlbumToPhoto < ActiveRecord::Migration
  def self.up
    add_column :photos, :album_id, :integer
  end

  def self.down
    remove_column :photos, :album_id
  end
end

Or:

class AddAlbumToPhoto < ActiveRecord::Migration
  def self.up
    change_table :photos do |t|
      t.references :album
    end
  end

  def self.down
    change_table :photos do |t|
      t.remove :album_id
    end
  end
end

Or if you insist on generating the code:

rails g migration add_album_to_photo album_id:integer