title: Using Primary Keys as Index
body: <p>In my application I usually use my primary keys as a way to access data. However, I've been told in order to increase performance, I should index columns in my table. But I have no idea what columns to index.</p>
  <p><strong>Now the Questions:</strong></p>
  <ol>
  <li><p>Is it a good idea to create an index on your primary key?</p>
  </li>
  <li><p>How would I know what columns to index?</p>
  </li>
  </ol>