title: Apply a SUM function on the product of two fields in InfluxDB
body: <p>I have the following query:</p>
  
  <pre><code>SELECT sum("field1" * "field2") FROM "my_db"."autogen"."data" GROUP BY time(1d) FILL(null)
  </code></pre>
  
  <p>In short I would like to perform the operation <code>sum</code> on the product of two fields <code>field</code> and <code>field2</code>.</p>
  
  <p>The above query returns an error: <code>expected field argument in sum()</code>.</p>
  
  <p>Is this kind of thing at all possible in InfluxDB?</p>