title: Create a group from two columns
body: <p>I have this:</p>
  
  <pre><code>Column1  Column2  Column3
  Water    1        2€
  Water    2        3€
  Water    2        5€
  Milk     1        8€
  Milk     1        4€
  Milk     2        10€
  Milk     3        1€
  </code></pre>
  
  <p>I am trying to group a column and sum the column to the side referring to the price.</p>
  
  <p>And I want this:</p>
  
  <pre><code>Column1  Column2  Column3
  Water    1        2€
  Water    2        8€
  Milk     1        12€
  Milk     2        10€
  Milk     3        1€
  </code></pre>
  
  <p>How can I do this?</p>