title: Retrieve the key of a node base on child
body: <p>I'm trying to get the key of a node based on the child. Here's my structure</p>
  
  <p>Code:</p>
  
  <pre><code>RESTAURANTS
      KTNfWKLD0isCsrpys
          name: “McDonalds”
          loc: “LA”
      KTNfWILD0iIkLLekc
          name: “KFC”
          loc: “LV”
  </code></pre>
  
  <p><strong>Code:</strong>  </p>
  
  <pre><code>FIRDatabase.database().reference().child("RESTAURANTS").queryOrderedByChild("name").queryEqualToValue("McDonalds").observeEventType(.Value, withBlock: { (snapshot) in
      print(snapshot.key)
  }, withCancelBlock: nil)  
  </code></pre>
  
  <p>How can I get the key of "McDonalds" in a query?</p>