title: kdb update statement
body: <p>Looked at all the documentation. Why is this not working? Loaded sp.q sample file given with KDB distribution. I am unable to figure out whats wrong with this statement.</p>
  
  <pre><code>q) \l sp.q
  q)trade
  date       sym time         price    size
  -----------------------------------------
  2007.07.23 a   04:48:52.665 73.53941 1000
  2007.07.23 a   04:48:52.675 81.73358 600
  2007.07.23 a   04:48:52.725 78.79526 900
  2007.07.23 a   04:48:52.735 79.59502 600
  2007.07.23 b   04:48:52.655 84.59765 200
  2007.07.23 b   04:48:52.685 98.36199 500
  2007.07.23 b   04:48:52.705 97.49875 700
  2007.07.23 c   04:48:52.645 61.48308 900
  2007.07.23 c   04:48:52.695 61.53192 700
  2007.07.23 c   04:48:52.715 71.95405 200
  
  q)trade:update size:300 from trade where sym=`c,price&gt;71
  'par
  q)trade
  date       sym time         price    size
  -----------------------------------------
  2007.07.23 a   04:48:52.665 73.53941 1000
  2007.07.23 a   04:48:52.675 81.73358 600
  2007.07.23 a   04:48:52.725 78.79526 900
  2007.07.23 a   04:48:52.735 79.59502 600
  2007.07.23 b   04:48:52.655 84.59765 200
  2007.07.23 b   04:48:52.685 98.36199 500
  2007.07.23 b   04:48:52.705 97.49875 700
  2007.07.23 c   04:48:52.645 61.48308 900
  2007.07.23 c   04:48:52.695 61.53192 700
  2007.07.23 c   04:48:52.715 71.95405 200
  </code></pre>