title: How to Calculate Daily Active Users(DAU) in big query to get the same result as Firebase Analytics dashboard
body: <p>I'm calculating DAU using the following query in <code>Big Query</code></p>
  <pre><code>select  count(user_pseudo_id)as DAU from 
                  (
                      SELECT user_pseudo_id FROM
                      `myProj.mydataset.events_*`
                      WHERE       
                      _TABLE_SUFFIX BETWEEN '20210504' AND '20210504'
                      and LOWER(platform) = 'android'
                      and event_name like 'session_start'
                      group by user_pseudo_id
                  )
  </code></pre>
  <p>And for the specified date I get <code>17748</code> as a result.
  For the same date Firebase shows <code>17186</code></p>
  <p>I want to understand how actually Firebase calculates this value, since
  the count of <code>session_start</code> event both in Firebase and Big Query DB is the same <code>25890</code></p>