title: Why does <> 'null' works in MySQL?
body: <p>Hope the question is not too generic. Couldn't find anything on the site or in SQL documentation:</p>
  
  <p>While coding, i tested this, and to my surprise it worked:</p>
  
  <pre><code>SELECT * FROM cal_entry WHERE cal_entry.parent_id &lt;&gt; 'null'
  </code></pre>
  
  <p>It actually shows the rows without the ones with <code>NULL</code> values (these are real <code>NULL</code> values in database, not strings with <code>'null'</code> inside).</p>
  
  <p>According to the docs, I should have used <code>NOT NULL</code>, of course. By the way, it doesn't work with <code>= 'null'</code>, like it is correctly stated in the docs.</p>
  
  <p>Can someone explain that?</p>