title: Total Sessions in BigQuery vs Google Analytics Reports
body: <p>I'm just learning BigQuery so this might be a dumb question, but we want to get some statistics there and one of those is the total sessions in a given day.</p>
  
  <p>To do so, I've queried in BQ:</p>
  
  <pre><code>select sum(sessions) as total_sessions from (
    select
      fullvisitorid,
      count(distinct visitid) as sessions,
      from (table_query([40663402], 'timestamp(right(table_id,8)) between timestamp("20150519") and timestamp("20150519")'))
      group each by fullvisitorid
  )
  </code></pre>
  
  <p>(I'm using the <code>table_query</code> because later on we might increase the range of days)</p>
  
  <p>This results in <code>1,075,137</code>.</p>
  
  <p>But in our Google Analytics Reports, in the "Audience Overview" section, the same day results:</p>
  
  <p><code>This report is based on 1,026,641 sessions (100% of sessions).</code></p>
  
  <p>There's always this difference of roughly ~5% despite of the day. So I'm wondering, even though the query is quite simple, is there any mistake we've made? </p>
  
  <p>Is this difference expected to happen? I read through BigQuery's documentation but couldn't find anything on this issue.</p>
  
  <p>Thanks in advance,</p>