title: Change a column in PowerQuery based on another column
body: <p>I try to make in Excel PowerQuery the equal Operation to SQL Operation:</p>
  
  <pre><code>SET ColumnA = "Max" WHERE ColumnC = "George" 
  </code></pre>
  
  <p>I know that I can <code>CREATE</code> a new <code>Colum</code>n with an the <code>M</code> expression </p>
  
  <pre><code>if ColumnA = "Max" then "George" Else "something" 
  </code></pre>
  
  <p>but I don't like to create a third column as I do it again and again.</p>
  
  <p>Any ideas how I could do this ? </p>