title: How to "update" a column using pig latin
body: <p>Imagine I have the following table available to me:</p>
  
  <pre><code>A: { x: int, y: int, z: int, ...99 other columns... }
  </code></pre>
  
  <p>I now want to transform this, such that <code>z</code> is set to <code>NULL</code> where <code>x &gt; y</code>, with the resulting dataset to be stored as <code>B</code>.</p>
  
  <p>and I want to do it without having to explicitly mention all the other columns, as this becomes a maintenance nightmare.</p>
  
  <p>Is there a simple solution?</p>