title: Android Firebase database, check if values exist
body: <p>I'm still learning the basics of android and firebase coding.</p>
  
  <p>I have two problems to tackle: </p>
  
  <ul>
  <li>I need to check if a school from my database exists before
  continuing.</li>
  <li>I need to verify that a username entered by a user isn't already in use (all lowercase).</li>
  </ul>
  
  <p>My database looks like this:</p>
  
  <pre><code>app: {
      school: {
          school: "university one"
          school: "university two"
          school: "university three"
      },
      users: {
          "some-user-uid": {
              school: "university one"
              username: "myname"
          }
      }
  }
  </code></pre>
  
  <p>Thank you.</p>