title: How to filter null value in Oracle sql
body: <p>I want to filter the records that <em>COMMENTS</em> attribute is null</p>
  
  <p><a href="https://i.stack.imgur.com/ImnVo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ImnVo.png" alt="enter image description here"></a></p>
  
  <p>I have tried </p>
  
  <pre><code>SELECT TABLE_NAME, COMMENTS FROM 
      (SELECT TABLE_NAME, COMMENTS FROM (select * FROM user_tab_comments))
      WHERE COMMENTS != null;
  </code></pre>
  
  <p>But it didn't return the right output. How can I do it?</p>