title: To calculate percentage value
body: <p>I have data as below..</p>
  
  <pre><code>count              ID
  ----------------------
  10                 1
  20                 2
  30                 4
  </code></pre>
  
  <p>How can I achieve the third column which calculates the percentage in oracle.</p>
  
  <pre><code>count              ID   %
  -------------------------------------
  10                 1    10/(10+20+30)
  20                 2    20/(10+20+30)
  30                 4    30/(10+20+30)
  </code></pre>