How to do sum with querying data on firebase
<p>I am trying to do sum with querying data.
I am using ionic and firebase.
My data is simple like:</p>

<pre><code>vitaly:{count:2,group:1}
kristina:{count:1,group:2}
yuri:{count:1,group:1}
dana:{count:1,group:3}
mark:{count:4,group:1}
</code></pre>

<p>is possible to get sum of count by group like: 
group:1 count:7
.....</p>

<p>Thanks!</p>