title: Joining two DataFrames in Spark SQL and selecting columns of only one
body: <p>I have two DataFrames in Spark SQL (<strong>D1 and D2</strong>). </p>
  
  <p>I am trying  to inner join both of them <code>D1.join(D2, "some column")</code> 
  and get back data of <strong>only D1, not the complete data set</strong>. </p>
  
  <p>Both D1 and D2 are having the same columns.</p>
  
  <p>Could some one please help me on this?</p>
  
  <p>I am using Spark 1.6.</p>