title: How to get the total value for distinct columns?
body: <p>How to get the total value for distinct coloumns ?</p>
  
  <pre><code> ------------------------------------------------------
  | order_no    |    company  | destination  |  total   |
  |-------------|-------------|--------------|----------|
  |     100     | Burger King | Los Angeles  | 100      |
  |-------------|-------------|--------------|----------|
  |     100     | Burger King | Phoenix      | 100      |
  |-------------|-------------|--------------|----------|
  |     101     | Burger      | Los Angeles  | 101      |
  ------------------------------------------------------
  </code></pre>
  
  <p>I mean the total value for order_no 100 is 200 . Like that. How can I get this ?</p>