Re: Detection of which attributes should get set in update trigger

Thanks for the reply. I confirm the behaviour. Your explanation makes
sense if I consider having read that with an update the is a complete
new record version written.

Am 10.11.2023 um 14:35 schrieb David G. Johnston:
> On Friday, November 10, 2023, Thiemo Kellner
> <thiemo(at)gelassene-pferde(dot)biz> wrote:
>
> Hi all
>
> I have a view, that is a join over 4 tables (the setup of the rule
> question). I want to update the central table over the view (by an
> instead-of trigger). How can I determine, whether an attribute
> should get set to NULL, "new.XYZ is null" or whether it should be
> left alone. Is there a leave-me-alone function determining,
> whether an attribute is in the set clause of an update statement.
> I am thinking along the line code in the trigger function like
>
> update TABLE
>    set XYZ = case
>                   when leave-me-alone (new.XYZ) then old.XYZ
>                   else new.XYZ
>              end;
>
> And what about the where condition... hm, guess I am a bit confused.
>
>
> IIUC, The NEW record is complete, with every value as it should be in
> the newly saved tuple.  There is no leave-me-alone concept.  You don’t
> get to know if the column was specified or not in the update command.
>
> David J.
>