title: Hive url parsing
body: <p>I have a question about parsing url using hive 
  For example, I have a table of urls,</p>
  
  <ol>
  <li><p><a href="http://xxxx.com&amp;key1" rel="nofollow noreferrer">http://xxxx.com&amp;key1</a> = 1&amp;key2 = 2&amp;key4 = 4</p></li>
  <li><p><a href="http://xxxx.com&amp;key1" rel="nofollow noreferrer">http://xxxx.com&amp;key1</a> = 1&amp;key2 = 2&amp;key3 = 3 &amp;key 4 = 4</p></li>
  <li><p><a href="http://xxxx.com&amp;key1" rel="nofollow noreferrer">http://xxxx.com&amp;key1</a> = 1&amp;key5 = 5</p></li>
  <li><p>http://.....</p></li>
  <li><p>http://....</p></li>
  </ol>
  
  <p>I need a output like this </p>
  
  <pre><code>key1  key2  key3  key4
   1     2    null   4
   1     2      3    4
   1    null  null   5
  </code></pre>
  
  <p>....
  ...</p>
  
  <p>I don't know the number of possible keys.
  How can I get this? </p>
  
  <p>Thank you!</p>