title: Firebase: Get the first result and update it
body: <p>I would like to create into Firebase an "AccountQueues" object that will have account and names or the word "FREE" if it doesn't have account.</p>
  
  <p>AccountQueues
    -LEf-OrdKi65WG0NkQSG
     AccountID: 
      "GR215"
      Name: 
       "FREE"</p>
  
  <p>When a user register I would like to take the first FREE AccountID and update it with the name of the user. Thank you for your help. I am developing an ionic 3 mobile app with this functionality. </p>