title: Convert blank values to zero when using the Query function
body: <p>Is there a way to convert data going into a <code>query()</code> function so that blank/null values are converted to zero?</p>
  
  <p>I have a dataset with three columns:</p>
  
  <pre><code>Group    AC       Plan
  Comms    350      [blank]
  IT       50,000   85,000
  Rent     15,000   15,000
  Training [blank]  8,500
  </code></pre>
  
  <p>I want to query the set to find the difference between AC and Plan, <br>e.g.
  <code>=query('data', "select A, B-C",1)</code>. However, since the query omits blank cells when calculating <code>B-C</code>, the result is like this:</p>
  
  <pre><code>Group    Diff
  Comms    [blank]
  IT       -35,000
  Rent     0
  Training [blank]
  </code></pre>
  
  <p>When I wanted this:</p>
  
  <pre><code>Group    Diff
  Comms    350
  IT       -35,000
  Rent     0
  Training -8,500
  </code></pre>
  
  <p>Before you go wild: I am <strong>not</strong> able to change the source data (the incoming data is actually another <code>query()</code> using the <code>pivot</code> functionality). And the reason I need this to work is I use a <code>limit</code> clause to confine the results to only the top 25 and bottom 25 differences.</p>