title: Increment Oracle time in varchar field by a certain amount?
body: <p>We have times stored in an Oracle varchar(5) field.</p>
  
  <p>Times stored using HH24:MI (ie: 22:30, 10:15).   </p>
  
  <p>How can we run a query that will increase or decrease these times by a certain amount?  Ie: increase by one hour or decrease by 45 minutes.</p>