title: Firebase: Swift - Query value in child node without knowing the parent key
body: <p><a href="https://i.stack.imgur.com/y84Uy.png" rel="noreferrer"><img src="https://i.stack.imgur.com/y84Uy.png" alt="Example image of my firebase data"></a></p>
  
  <p>I have a firebase database which I have imported a list of approx. 8200 Universities with the details seen above.</p>
  
  <p>I want to be able to enter an email address into a text field then query the "domain" part of this JSON. My issue is I need to query all the domains in the list of 8000, however I do not know how to search domain ad I do not have the "7542" to use a <code>childByAppendingPath</code>.</p>
  
  <p>So I have a reference to "universities" but I need to be able to query "domain" without knowing the parent key (i.e. 7542 in the example above, but I want to search the domain, "iautb.ac.ir").</p>