title: smart way to generate unique random number
body: <p>i want to generate a sequence of unique random numbers in the range of 00000001 to 99999999.</p>
  
  <p>So the first one might be 00001010, the second 40002928 etc.</p>
  
  <p>The easy way is to generate a random number and store it in the database, and every next time do it again and check in the database if the number already exists and if so, generate a new one, check it again, etc.
  But that doesn't look right, i could be regenerating a number maybe 100 times if the number of generated items gets large.</p>
  
  <p>Is there a smarter way?</p>
  
  <p>EDIT
  as allways i forgot to say WHY i wanted this, and it will probably make things clearer and maybe get an alternative, and it is:
  we want to generate an ordernumber for a booking, so we could just use 000001, 000002 etc. But we don't want to give the competitors a clue of how much orders are created (because it's not a high volume market, and we don't want them to know if we are on order 30 after 2 months or at order 100. So we want to have an order number which is random (yet unique)</p>