title: Can I combine values of two rows if labels are not identical in pandas
body: <p>Here's the 2 dataframes I want to combine. But the labels are different from each other</p>
  <pre><code>df1
  Date        Campaign                              Sales
  11/07/2020  AMZ CT BR Leather Shoes ABCDEFG1234   $10
  11/07/2020  AMZ CT NB Leather Shoes ABCDEFG1234   $20
  11/07/2020  AMZ OG BR Bag HGIJK567                $30
  11/07/2020  AMZ OG NB Bag HGIJK567 Desktop        $40
  
  df2
  Date        Campaign                              Spend        
  11/07/2020  GA BR Leather Shoes ABCDEFG1234       $5
  11/07/2020  GA NB Leather Shoes ABCDEFG1234       $6
  11/07/2020  GA BR Bag HGIJK567                    $7
  11/07/2020  GA NB Bag HGIJK567 Desktop            $8
  </code></pre>
  <p>Here's the output I want</p>
  <pre><code>df3
  Date        Campaign                         Spend   Sales
  11/07/2020  CT BR Leather Shoes ABCDEFG1234  $5      $10
  11/07/2020  CT NB Leather Shoes ABCDEFG1234  $6      $20
  11/07/2020  OG BR Bag HGIJK567               $7      $30
  11/07/2020  OG NB Bag HGIJK567 Desktop       $8      $40
  
   
  </code></pre>