title: mysql - count letters
body: <p>Can anyone tell me how to count the letters in a string in MySQL?</p>
  
  <p>For example:</p>
  
  <pre><code>SELECT numberOfLetters('abc123 def')
  </code></pre>
  
  <p>would return 6</p>
  
  <p>By letter, I mean A-Z and a-z.</p>
  
  <p>numberOfLetters is not valid SQL of course, but it illustrates what I am trying to do.</p>
  
  <p>The version of MySQL that I'm using is 5.5.27</p>