title: row operation in same table and same coloumns
body: <p>i have a little problem to discuss i hope it will easy for you.
  suppose i have table A with 2 columns as</p>
  
  <pre><code>item          price
  milk           25
  milk           50
  milk           100
  Butter         25
  Butter         100
  Butter         200
  </code></pre>
  
  <p>now i want to display a table B derived from table A as</p>
  
  <pre><code>item          price growth rate
  milk           0
  milk           100
  milk           100
  Butter        100
  Butter         200
  Butter         100
  </code></pre>
  
  <p>formula for growth rate for row1 is </p>
  
  <pre><code>((row[1]-row[0])/row[0])*100
  eg for 1st row ((50-25)/25)*100
  </code></pre>
  
  <p>can you suggest a SQl Query for it</p>