"Jonas Forsman" <jfo123@hotmail.com> writes:
> sql:
> UPDATE user SET comment= E'[2011-11-16] Note to myself no: 171\\n' ||
> comment WHERE userid=1
> This query fails if comment is an empty string or null.
Define "fails".
Personally I'm wondering whether you remembered that concatenation of a
null with something else yields null. You might possibly want to spell
the above as SET comment = '...' || coalesce(comment, null) ..., if you
want to pretend that a null is the same thing as an empty string.
regards, tom lane