title: Empty string vs NULL
body: <p>I've a table where some rows have some blank <code>cells</code>. I tried to select such rows using IS NULL function. But the query select 0 rows. </p>
  
  <pre><code>select * from zzz_fkp_registration_female where fname is null;
  (0 row(s) affected)
  </code></pre>
  
  <p>Now I changed my query to:</p>
  
  <pre><code>select * from zzz_fkp_registration_female where fname is null or fname ='';
  </code></pre>
  
  <p>I got the desired result. </p>
  
  <p>Why is IS NULL not giving the result? What is the difference between <code>IS NULL</code> and <code>''</code> since the cells are empty. Please explain.</p>