title: How to generate the effective order number? (nice pattern with unpredicatable gap)
body: <p>just wondering does anyone in here have good idea about generating nice order id?</p>
  
  <p>for example</p>
  
  <p>832-28-394, which show a quite nice and formal order id (rather than just use an database auto increment number like ID=35).</p>
  
  <p>the order id need to look random so it can  not be able to guess by user.</p>
  
  <p>e.g.  832-28-395  (shoudnt exist) so there will always some gap between each id.</p>
  
  <p>just like the account number for your bank card?</p>
  
  <p>Cheers</p>