title: How to combine aggregates within a group with aggregates across groups within SSRS
body: <p>With this dataset:</p>
  
  <pre><code>Category | Amount
  A        | 5
  A        | 3
  B        | 6
  B        | 2
  B        | 1
  C        | 7
  </code></pre>
  
  <p>I want to create a tablix grouping on category, displaying the percentage of the total amount:</p>
  
  <pre><code>Category | Percentage
  A        | 33%
  B        | 38%
  C        | 29%
  </code></pre>
  
  <p>Which should be a simple calculation:</p>
  
  <pre><code>Category | Percentage
  A        | ((Sum of Amount within group / Sum of Amount across groups) * 100)%
  B        | ((Sum of Amount within group / Sum of Amount across groups) * 100)%
  C        | ((Sum of Amount within group / Sum of Amount across groups) * 100)%
  </code></pre>
  
  <p>But I can't figure out how to do that within Report Designer (SSRS) - whenever I create a row grouping on <code>Category</code>, I can get the sum within the group with <code>=Sum(Fields!Amount.Value)</code>. But how to get the sum across groups from a cell within the group?</p>