title: How to update child node data in Firebase Database?
body: <p>Actually I have a database,in which there are multiple users. Each user has his own data,which also includes an array of objects of type "Task".What I want to do is update a particular task's data .I tried  <code>ref.child (userId).child ("Tasks").child ("done").setValue (isDone);</code> ,but a new entry is added in the database.So my question is ,how to update the child node's data when we don't know the UID of that node ? I'm adding the snapshot of my database,here the users have UID and under that there is TASKS which contains task's data ,so I have to update the particular task's data ,hoe to do that?? Please help.</p>
  
  <p><a href="https://i.stack.imgur.com/v0IAo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/v0IAo.png" alt="enter image description here"></a></p>
  
  <p>I tried Peter's solution, but the data is getting updated as follows:</p>
  
  <p><a href="https://i.stack.imgur.com/xmE80.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xmE80.png" alt="enter image description here"></a></p>
  
  <p>But only the "done" should be updated.</p>