title: Pandas join 2 dataframes
body: <p>I have 2 dataframes:</p>
  
  <pre><code>&gt;&gt;&gt; result
           id   order_nr
  0   3131334  334756912
  0   3131312  386517432
  0   3131309  356299432
  0   3131205  397514312
            ...
  
  &gt;&gt;&gt; OMSdf
       order_nr            status  refund_amount
  0   377766482  already_canceled              0
  1   348722582  already_canceled              0
  2   395287472           on_hold              0
  3   345883652  already_canceled              0
            ...
  </code></pre>
  
  <p>Those 2 dataframes have some common values in the field "order_nr":</p>
  
  <pre><code>&gt;&gt;&gt; result[result['order_nr'] == '377766482']
          id   order_nr
  0  3129153  377766482
  
  &gt;&gt;&gt; OMSdf[OMSdf['order_nr'] == '377766482']
      order_nr            status  refund_amount
  0  377766482  already_canceled              0
  </code></pre>
  
  <p>But I try to join them together:</p>
  
  <pre><code>resultfinal = result.join(OMSdf, on='order_nr', how='inner', lsuffix='', rsuffix='_oms', sort=False)
  </code></pre>
  
  <p>the result is empty:</p>
  
  <pre><code>&gt;&gt;&gt; resultfinal
  Empty DataFrame
  Columns: [id, order_nr, order_nr_oms, status, refund_amount]
  Index: []
  </code></pre>