title: Firebase Query: equalTo on a list
body: <p>We are building an android app that needs to synchronize phone contacts with people already registered on the app. We are using firebase</p>
  
  <p>To do this, we'd like to retrieve a list of existing users based on their phone numbers.</p>
  
  <p>I have managed to retrieve users based on their phone number with ref.orderByChild("phone").equalTo($phoneNumber)</p>
  
  <p>But I am wondering if there is a way of passing a list of phone numbers, instead of querying for each phone number one at a time ?
  Something like this:
  ref.orderByChild("phone").isIn([phone1, phone2, phone3])</p>
  
  <p>I am just beginning to learn Firebase but I love the concept :)
  Thanks a lot for your answers!</p>