title: MySQL: problem to build multiple mysql select
body: <p>i have a problem to build multiple mysql select. I am a german guy, i hope my english is enough to explain. I know already, that this:</p>
  
  <pre><code>$mysqli-&gt;prepare("
  SELECT gender
       , age
       , education
       , department
       , code_numbers
    FROM ".TABLE_ANSWERS_BASIC_SELECT." 
  WHERE gender = 'female' 
     AND gender = 'male'
  ")
  </code></pre>
  
  <p>not work.</p>
  
  <p>How i can do this? I need to create the WHERE with checkboxes, so the WHERE is on the fly.</p>
  
  <p>I did read a lot answer here about this, but nothing works for me.
  Thank you in advance for help.</p>