title: a sql query to compare results of following queries
body: <pre><code>SELECT pd_end_dt,SUM(nrx_cnt) Total_Count
  FROM wkly_lnd.lnd_wkly_plan_rx_summary
  WHERE pd_end_dt &gt;= '01-Sep-08' AND pd_end_dt &lt; '30-Sep-08'
  GROUP BY pd_end_dt
  
  SELECT pd_end_dt,SUM(nrx_cnt) Total_Count
  FROM wkly_lnd.lnd_wkly_plan_rx_summary
  WHERE pd_end_dt &gt;= '01-Sep-07' AND pd_end_dt &lt; '30-Sep-07'
  GROUP BY pd_end_dt
  </code></pre>
  
  <p>the result set on running each query will be like</p>
  
  <pre>
  09/28/2007 00:00:00 702,457.36
  09/21/2007 00:00:00 703,604.59
  09/07/2007 00:00:00 636,619.92
  09/14/2007 00:00:00 698,082.03
  </pre>
  
  <p>similarly for previous year </p>
  
  <p>I need to calculate the difference of units sold as compared to last year and also to add one column which will find percentage change </p>