title: Firebase database how to get nodes on based of the child value?
body: <p>Actually i want to get online users only not the whole list of users.
  This is my database structure:</p>
  
  <pre><code>Users
      - Uid
          - online : true
  </code></pre>
  
  <p>i want to get list of users which are online without needing to get each one of the user and then sorting it by checking the datasnapshot.</p>