title: Apache NiFi: How to compare multiple rows in a csv and create new column
body: <p>I have a csv which looks like this.</p>
  
  <pre><code>Jc,TXF,timer,alpha,beta
  15,44,55,12,33
  18,87,33,111
  9,87,61,29,77
  </code></pre>
  
  <p>Alpha and Beta combined makes up a city code. I want to add the name of the city to the csv as a new column.</p>
  
  <pre><code>Jc,TXF,timer,alpha,beta,city
  15,44,55,12,33,York
  18,87,33,111,London
  9,87,61,29,77,Sydney
  </code></pre>
  
  <p>I have another csv with only the columns <code>alpha,beta,city</code>. Which looks like this:</p>
  
  <pre><code>alpha,beta,city
  12,33,York
  33,111,London
  29,77,Sydney
  </code></pre>
  
  <p>How can I achieve this using Apache NiFi. Please suggest the processors and workflow needed to be used to achieve this.</p>