title: Ruby on Rails DB Migration Script Using Text instead of :string varchar
body: <p>I'm a beginner at Ruby on Rails so I apologize if this is quite obvious, but I'm trying to learn how to write the database migration scripts and I'd like to change the following long_description to a text value instead of string:</p>
  
  <pre><code>class CreateArticles &lt; ActiveRecord::Migration
    def self.up  
      create_table :articles do |t|
        t.column "short_description", :string
        t.column "long_description", :string
        t.timestamps
      end
    end
  end
  </code></pre>
  
  <p>Any ideas how this is possible?</p>