amy cheng wrote:
>
> hi, all experts there,
>
> it's me again :-)
oh well :)
> I'm studying the example in postgresql-6.5.1/src/pl/plpgsql/test.
> I have another question: why do we need to "Set backlink to empty string if
> NULL value given"? is it JUST a test, or, some reasons to
> do that in general?
Nope, it's just an example of "triggers".
You should also post the CREATE statement of PSlot,
does it have a "NOT NULL" constraint for backlink attribute?
if yes, you've got the answer (I would also have a look but
I'm on the other OS right now :> )
> -- ************************************************************
> -- * BEFORE INSERT or UPDATE on all slots with backlink
> -- * - Set backlink to empty string if NULL value given
> -- ************************************************************
> create function tg_chkbacklink() returns opaque as '
> begin
> if new.backlink isnull then
> new.backlink := '''';
> end if;
> return new;
> end;
> ' language 'plpgsql';
>
> create trigger tg_chkbacklink before insert or update
> on PSlot for each row execute procedure tg_chkbacklink();
>
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