title: Substring ERROR: argument of WHERE must be type boolean, not type text
body: <pre><code>SELECT substring(category FROM '[0-9]+') from microwaves;
  </code></pre>
  
  <p>This works fine and returns the microwave categories that are numeric.</p>
  
  <pre><code>UPDATE microwaves SET category = '' WHERE substring(category FROM '[0-9]+');
  </code></pre>
  
  <p>This throws an error in Postgres 9.5</p>
  
  <blockquote>
    <p>ERROR:  argument of WHERE must be type boolean, not type text</p>
  </blockquote>
  
  <p>How can I update the numeric fields?</p>