title: How to change a column type of a BigQuery table by querying and exporting to itself?
body: <p>I have a <code>integer</code> type column in my BigQuery table and now I need to convert it to a <code>float</code> column. I also have to keep all records. What I want to do is <strong><em>changing the column type</em></strong>. Not casting.</p>
  
  <p>I've read that it's possible to do it just by exporting results of a query on a table to itself.</p>
  
  <p>How to do it?</p>