Ben Chobot <bench(at)silentmedia(dot)com> writes:
> Say I have:
> create t (c1 int not null, c2 int);
> Is it possible to create an update trigger on t such updates will only
> be allowed if the update statement explicitly sets c1, even if the new
> value is the same?
No. A trigger can only tell whether the old and new values are the same
or not, not why they are that way.
regards, tom lane