Am Dienstag, 10. Januar 2006 16:01 schrieb Tom Lane:
> That's because SHOW does the same thing. SHOW has a little problem in
> that it can't readily show the difference between "null" and an empty
> string, so while I find the behavior pretty ugly, I don't have a better
> idea.
Since SHOW is primarily for "showing", I'd expect that that user can apply the
visualization tweaks that the frontend provides, for instance \pset in psql,
to tell apart null values and empty strings. Not that "unset" is a typical
value for string parameters, but you can see where I might go here.
Moreover, the unset state shouldn't exist at all. No parameter can behave
reasonably if unset behaved differently from an empty string. Explicitly
assigning an unset state doesn't work. So it seems that for all external
communication, an unset string parameter should simply display the empty
string.
--
Peter Eisentraut
http://developer.postgresql.org/~petere/