DataFrame and Dataset : <p>In spark,there always be operation like this:</p>

<pre><code> hiveContext.sql("select * from demoTable").show()
</code></pre>

<p>When I look up the <strong><em>show()</em></strong> method in Spark Official API,the result is like this:
<a href="https://i.stack.imgur.com/wyzV2.png" rel="nofollow noreferrer">enter image description here</a>
 And when I change the key word to 'Dataset',I Find that the method used on DataFrame belongs to Dataset. How does it happen? Is there any implication? </p>
