title: How do a simultaneous ascending and descending sort in KDB/Q
body: <p>In SQL, one can do</p>
  
  <pre><code>SELECT from tbl  ORDER BY col1, col2 DESC
  </code></pre>
  
  <p>In KDB, one can do </p>
  
  <pre><code>`col1 xasc select from tbl
  </code></pre>
  
  <p>or </p>
  
  <pre><code>`col2 xdesc select from tbl
  </code></pre>
  
  <p>But how does one sort by col1 ascending then by col2 descending in KDB/Q?</p>