title: How to check for uppercase letters in MySQL?
body: <p>I want to check, if a string consits only of uppercase letters. I know that RLIKE/REGEXP are not case sensitive in MySQL. So I tried to use the <code>:upper:</code> character class:</p>
  
  <pre><code>SELECT 'z' REGEXP '^[[:upper:]]+$';
  </code></pre>
  
  <p>This gives true, although the z is in lower case,... why?</p>