title: Get total of rows with SUM GROUP BY
body: <p>I'm trying to get the total of subtotal that I get from a <code>SUM</code> and <code>GROUP BY</code> query. </p>
  
  <p>Here is my query so far:</p>
  
  <pre><code>  SELECT SUM(opportunite_montant_ht)*(stade_pourcentage/100) 
        As subtotal
      FROM opportunite O 
      JOIN opportunite_stade OS 
        ON O.opportunite_stade=OS.stade_id
  GROUP BY stade_id
  </code></pre>
  
  <p>And the result:</p>
  
  <pre><code>subtotal
  
  35100.0000
  
  330.0000
  </code></pre>
  
  <p>Now how can I get only the total of these subtotals with my query?</p>