Scott Marlowe wrote:
> Since you can check which columns have changed, it's pretty easy to
> write a trigger that just skips its logic when none of the trigger
> columns have changed.
I think column-level triggers actually fire when one of the columns is
written to, not only when the value there is distinct from the previous
one. This small difference is not easy to emulate by comparing OLD and
NEW in the trigger body. Details might need to be checked in the
standard and existing implementations.