title: How to avoid computed-column duplicate computation in an SQL Query
body: <p>I have the following query:</p>
  
  <pre><code>Use Northwind 
  
  select OrderID as 'Order ID', (UnitPrice * Quantity) as 'Total', case
  when (UnitPrice * Quantity) &gt; 100 then 'Good' else 'Bad'
  end as 'Rating' from [Order Details]
  </code></pre>
  
  <p>Theoretically, it computes <code>(UnitPrice * Quantity)</code> two times, and I believe that this is a bad choice for the performance.</p>
  
  <p>How to accomplish this (avoiding the duplicate computation) in an elegant way?</p>