title: Get total amount invoiced by salesperson code by customer
body: <p>How do I get a total <code>Amount</code> invoiced by <code>Salesperson Code</code> by <code>Customer</code> given the following query?</p>
  
  <pre><code>SELECT  l.[Customer No_], c.[Name], l.[Amount], c.[Salesperson Code], l.[Posting Date]
  FROM    [Service Invoice Line] l join [Customer] c on 
          l.[Customer No_] = c.[No_]
  Where   l.[Posting date] &gt;= '10-01-2012'
          and c.[Salesperson Code] &gt; ''
  Group by l.[Customer No_],c.[Name],c.[Salesperson Code],l.[Amount],l.[Posting Date]
  Order by l.[Customer No_]
  </code></pre>