title: How to get count of elements in columnA which are not present in ColumnB
body: <p>I have two columns:</p>
  
  <pre><code>A         B
  Hello    Good
  How      Hello
  Are      Morning
  You      You
  </code></pre>
  
  <p>I want the count of elements in A which are not present in B (<code>How , Are</code> here), The answer would be 2 in this case.</p>