title: How to find sum of count, grouped by the id?
body: <p>I would like to get the output for the following problem.
  I have the following datatype:</p>
  
  <pre><code>id      start        end       count     Time      Train
  001     Paris      London        01      05:00      Yes
  001     Paris      London        01      05:00      Yes
  002     Prague     Vienna        15      15:00      No
  003     Frankfurt  London        01      17:00      Yes
  015     Paris      London        08      21:00      No
  019     Barcelona  Vienna        15      15:00      No
  003     Frankfurt  London        01      07:00      Yes
  002     Prague     Vienna        15      05:00      No
  </code></pre>
  
  <p>I would like to find the sum of count, grouped by the id. Also ignore the rows that has the same id, start and end . Also I have a data of 4 gb and I would like to find the start and end city of top 5 count. Thank you.</p>
  
  <p>I could like to get output that gives data something similar to this,</p>
  
  <pre><code> Prague -&gt; Vienna     Count : 15
   Barcelona -&gt; Vienna  count : 15
   Paris --&gt; london     Count : 09
   Frankfurt -&gt; London  Count:  02
  .....
  </code></pre>