title: How can I define regular expression and to make sure that it contains a certain character?
body: <p>I have to define a Membership ID which is a string of 3 characters which can have lower/upper case letters and digits. </p>
  
  <p>For instance AA2 and 2AA or  A22 are valid regular expressions.  It does not matter the position, I need to make sure there is at least one digit in the string. </p>
  
  <p>The current expression is this <code>([a-z]|[A-Z]|[0-9]){3}</code> . What should I add as a "condition" to look for a digit?</p>
  
  <p>Thank you in advance,
  Liviu</p>