[SQL] Don't want blank data

[David Olbersen]

Greetings,
  Is there a way to have postgresql always return a value for each row
  requested? To be more clear, if I were using a Perl SQL hybrid I would write
  something like

  SELECT computer_ip or 'unset' FROM computers;

  So that if computers.computer_ip is NULL or '' I will get 'unset' back from
  the database. I hope this makes sense and somebody can point me in a good
  direction

-- Dave