title: Combing rows based on a count, adding values
body: <p>Here's the dilemma: I have a table with rows. I need to count based on frequency of a certain value (in the eMail column), and then ADD numbers in certain column (cost)... as an example</p>
  
  <pre><code>mail           cost
  me@me.com      10
  me@me.com      5
  john@john.com  3
  me@me.com      7
  john@john.com  2
  </code></pre>
  
  <p>So I need to group rows based on the email address, and add the numbers in the grouped rows "cost" column. The results should come out as an array:</p>
  
  <pre><code>email          frequency  totalCost
  me@me.com      3          22
  john@john.com  2          5
  </code></pre>