title: MySQL - How to make a statement AND IFNULL
body: <p>how do I make this statement <code>AND IFNULL</code>?</p>
  
  <p><code>TIMESTAMPDIFF(YEAR,a.date_of_birth,CURDATE()) &gt;=  '' AND TIMESTAMPDIFF(YEAR,a.date_of_birth,CURDATE()) &lt;= ''</code>:</p>
  
  <p>Using <code>AND</code> or <code>OR</code> only messes my select statement. </p>