title: group all readings by day in BigQuery
body: <p>I am new to BigQuery and so I'm struggling with grouping my data in a way that could be useful. At this point in time I have converted the unix timestamps to a date ( e.g 2018-08-27 04:54:56 UTC, etc...). I have readings every 10 minutes or so and would like to group them by date only and then take the daily average for my various columns. I think 'group by' and then'avg' might be the way forward but I am unsure how to implement the first part. The code I have used so far to create my table is as follow:</p>
  
  <pre><code>  SELECT TIMESTAMP_SECONDS(timestamp) as timestamp,humidity,co2,temperature,app_id
    FROM data.staging 
    where timestamp is not null
    ;
  </code></pre>
  
  <p>and here are a few rows of what my output looks like:</p>
  
  <pre><code>|| Timestamp              || humidity  || co2   || temperature  || app id||
  
  ||========================||===========||=======||==============||========||
  
  ||2018-08-31 13:35:50 UTC || 63.4      || 634.5 || 21.2         || office_||
  
  ||2018-08-31 14:37:20 UTC || 67.8      || 600.4 || 20.8         || office_||
  </code></pre>
  
  <p>etc..</p>
  
  <p>Sorry for the poor formatting and if there's anything else needed I would be happy to provide. Thanks for any help!</p>