title: How to find net rows from sales and cancel rows using sql
body: <p>I have a table with columns mentioned below:</p>
  
  <pre><code>transaction_type  transaction_number  amount
  
  Sale                 2016040433         50
  Cancel               R2016040433       -50
  Sale                 2016040434         50
  Sale                 2016040435         50
  Cancel               R2016040435       -50
  Sale                 2016040436         50
  </code></pre>
  
  <p>I want to find net number of rows with only sales which does not include canceled rows.
  (Using SQL Only).</p>