title: Firebase - Retrieve property value by key
body: <p>E.g. - if referralId = <code>1OOdbg7u</code>, how would I retrieve the value 0 from the database.</p>
  
  <p><a href="https://i.stack.imgur.com/eRaSI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eRaSI.png" alt="enter image description here"></a></p>
  
  <p>This is my code so far:</p>
  
  <pre><code>  // referralId = 1OOdbg7u
  
    getNoOfReferredUsers(referralId) {
      if (referralId) {
        return this.afs.collection('waitlist', ref =&gt; ref.where(referralId, '&gt;=', 0)).valueChanges();
      }
    }
  </code></pre>