title: Get count percent of a record in a single query
body: <p>refer to this question:</p>
  
  <p><a href="https://stackoverflow.com/questions/7307808/get-count-of-items-and-their-values-in-one-column">Get count of items and their values in one column</a></p>
  
  <p>how I can get percent of record count in single query like this:</p>
  
  <pre><code>ItemId        count          Percent
  ------------------------------------
     1            2              33.3
     2            0                0
     3            1              16.6
     4            3              50.0            
  </code></pre>
  
  <p>thanks </p>