title: MuleSoft: Sum line items and group by ID
body: <p>I am new to integration and MuleSoft so I need your help. I have a flat file with different invoice line items per salesID, like this:</p>
  
  <pre><code>SalesOrderID    OrderQty    UnitPrice
  
  43659   70  2024.994
  
  43659   70  2024.994
  
  43660   1   419.4589
  
  43660   1   874.794
  
  43661   1   809.76
  </code></pre>
  
  <p>I want to insert total invoice amount and quantity in another CSV file using Mule, something like this:</p>
  
  <pre><code>SalesOrderID    OrderQty    UnitPrice
  
  43659   140 4049.988
  
  43660   2   1294.4589
  
  43661   1   809.76
  </code></pre>
  
  <p>I know how to do this in informatica,but im trying to figure out a way to do this in MuleSoft. How can I sum up all the line items and group them by SalesOrderID? Any help/clue will be really appreciated. 
  Thanks.</p>