title: Merging two dataframes on some overlapping columns while keeping non-overlapping columns
body: <p>I currently have two dataframes:</p>
  
  <pre><code>df1:
  
       col1    col2   col3   col4
   0  Apple   store1    1      3
   1  Tree    store2    1      3
   2  Banana  store3    2      4
   3  Card    store4    2      4 ...
  
  df2:
  
       col1    col2   col3   col4   col5   col6
   0  Apple   store1    1      3     123    50
   1  Tree    store2    1      3     451    32
   2  Mango   store2    2      4     313    15
   3  Guava   store5    2      4     113     9
  </code></pre>
  
  <p>What I want to do is to merge df1 and df2 together if the values in the first 4 columns are identical, but I want to append the values of col5 and col6 onto the merged dataframe. So the ideal output would be:</p>
  
  <pre><code>merged_df:
  
       col1    col2   col3   col4   col5   col6
   0  Apple   store1    1      3     123    50
   1  Tree    store2    1      3     451    32 ...
  </code></pre>
  
  <p>When I tried to merge I get NaN values returned on col5 and col6 on the merged dataframe. Any ideas please?</p>
  
  <p>Thanks</p>