title: Change column value in a dataframe spark scala
body: <p>This is how my dataframe looks like at the moment </p>
  
  <pre><code>+------------+
  |    DATE    |
  +------------+
  |    19931001|
  |    19930404|
  |    19930603|
  |    19930805|
  +------------+
  </code></pre>
  
  <p>I am trying to reformat this string value to yyyy-mm-dd hh:mm:ss.fff and keep it as a string not a date type or time stamp. </p>
  
  <p>How would I do that using the withColumn method ?</p>