title: How to add 0 (zero) for mobile number
body: <p>On the <code>mobile</code> field I have a list of mobile number starting with 7xxxxxxxxx</p>
  
  <p>I need a quick way to add 0 at the beginning, eg: 07xxxxxxx</p>
  
  <p>But it will need to check if 0 exist or not before updating</p>
  
  <p>Is it possible to do that by SQL query</p>