title: Use content of binary as string in DataFrame in pyspark
body: <p>I created a DataFrame from an existing table where two columns are stored as binary. For the further processing I need the binary-content as string.</p>
  
  <p>Example:</p>
  
  <pre><code>+--------------------+--------------------+
  |              DB_KEY|          PARENT_KEY|
  +--------------------+--------------------+
  |[00 50 56 88 0A]    |[00 50 56 88 12]    |
  
  Schema:
  root
   |-- DB_KEY: binary (nullable = true)
   |-- PARENT_KEY: binary (nullable = true)
  </code></pre>
  
  <p>Content of binary should be used as string like:<br></p>
  
  <pre><code>DB_KEY = "005056880A"
  PARENT_KEY = "0050568812"
  </code></pre>
  
  <p>Can you please give me any hints how to do this?</p>