title: How to Join the column which is present in the Same Table
body: <p>Actually im try to Join the column which is present on same table.
  Here is the scenario ,</p>
  
  <p>PROBLEM :</p>
  
  <pre><code>   Column_1   column_2  column_1_data   column_2_date
       null       null      data1         data2
       data       data       null          null
  </code></pre>
  
  <p>Expected Ouput:</p>
  
  <pre><code>   Column_1   column_2  
       data1      data2      
       data       data       
  </code></pre>