title: How to copy other column's value as default value for a new column in rails migration?
body: <p>I have a model with a column <code>price</code>. I need to add a new_column <code>marked_price</code> having value of <code>price</code> as it's default value. Can I write this in my migration, or what could be the best way to do this?</p>
  
  <p>Something like:</p>
  
  <pre><code>class AddMarkedPriceToMenuItems &lt; ActiveRecord::Migration
    def change
      add_column :menu_items, :marked_price, :decimal, :default =&gt; :price
    end
  end
  </code></pre>