change null to ""

hi, all experts there,

it's me again :-)

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?

Thanks!!!!!!!!!!!

amy

#################################################

-- ************************************************************
-- * 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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