title: Calculating grand totals from group totals in Reporting Services
body: <p>I have some data grouped in a table by a certain criteria, and for each group it is computed an average —well, the real case is a bit more tricky— of the values from each of the detail rows that belong to that group. This average is shown in each group footer rows. Let's see this simple example:</p>
  
  <p><img src="https://farm4.static.flickr.com/3008/2958165686_088405e1ef_o.jpg" alt="Report table"></p>
  
  <p>What I want now is to show a grand total on the <strong>table footer</strong>. The grand total should be computed by <em>adding</em> each group's average (for instance, in this example the grand total should be 20 + 15 = 35). However, I can't nest aggregate functions. How can I do?</p>