title: regex to check the string contains only letter and numbers but not only numbers
body: <p>I need a help with regex which checks the string contains only letter and numbers but not only numbers</p>
  
  <p>Valid</p>
  
  <pre><code>* letters
  * 1wret
  * 0123chars
  * chars0123
  * cha2rs
  </code></pre>
  
  <p>Invalid</p>
  
  <pre><code>* 1324
  * xcvxxc%$#
  * xcv123xxc%$#
  * _012chars
  * _test
  </code></pre>