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demo_app / db / migrate / 20111003131413_create_microposts.rb

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class CreateMicroposts < ActiveRecord::Migration
  def self.up
    create_table :microposts do |t|
      t.string :content
      t.integer :user_id

      t.timestamps
    end
  end

  def self.down
    drop_table :microposts
  end
end