title: postgres find zip codes near specific zip code
body: <p>Assuming a Postgres Table containing <code>zip</code> as <code>varchar(10)</code> I want to get either all results matching a specific zip or extend my results with entries close to the queried one in case there are not enough results. Say:</p>
  
  <p>A user searches for <code>zip</code> "56500" and my result-set returns 2 items running an exact match. In this case I want to perform a kind of <code>like</code> query that finds "565%" entries. Eventually I need to run this in one query.</p>
  
  <p>Any suggestions?</p>