Checking if a particular value exists in the Firebase database

Question

I am making an Android application using Firebase realtime database. When a new user registers on my app, that user\'s data is saved in the Firebase database. <

Answer 1

Instead of checking for the exists of the reference you can use orderBy query to check whether username exists already

orderByChild('username').equalTo(username) query would return data if some data already exists else it will return null.