title: Python: How to update (overwrite) Google BigQuery table using pandas dataframe
body: <p>I have a table in Google BigQuery(GBQ) with almost 3 million records(rows) so-far that were created  based on data coming from MySQL db every day. This data inserted in GBQ table using Python pandas data frame(<code>.to_gbq()</code>).</p>
  
  <p>What is the optimal way to sync changes from MySQL to GBQ, in this direction, with python.</p>