Re: [GENERAL] change null to "" - Mailing list pgsql-general

From Teodor Cimpoesu
Subject Re: [GENERAL] change null to ""
Date
Msg-id 37CC6BAF.7A40B175@digiro.net
Whole thread Raw
In response to change null to ""  ("amy cheng" <amycq@hotmail.com>)
List pgsql-general
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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