title: NULL vs empty string
body: <p>What is the difference between the below queries &amp; how it works?</p>
  
  <pre><code>SELECT * FROM some_table WHERE col IS NOT NULL 
  </code></pre>
  
  <p>&amp;</p>
  
  <pre><code>SELECT * FROM some_table WHERE col &lt;&gt; ''
  </code></pre>
  
  <p>Regards,
  Mubarak</p>