title: MongoDb query condition on comparing 2 fields
body: <p>I have a collection <code>T</code>, with 2 fields: <code>Grade1</code> and <code>Grade2</code>, and I want to select those with condition <code>Grade1 &gt; Grade2</code>, how can I get a query like in MySQL?</p>
  
  <pre><code>Select * from T Where Grade1 &gt; Grade2
  </code></pre>