title: Scala Spark DataFrame : dataFrame.select multiple columns given a Sequence of column names
body: <pre><code>val columnName=Seq("col1","col2",....."coln");
  </code></pre>
  
  <p>Is there a way to do dataframe.select operation to get dataframe containing only the column names specified . 
  I know I can do <code>dataframe.select("col1","col2"...)</code>
  but the <code>columnName</code>is generated at runtime.
  I could do <code>dataframe.select()</code> repeatedly for each column name in a loop.Will it have any performance overheads?. Is there any other simpler way to accomplish this?</p>