Обсуждение: Musings on Triggers

Greetings all,

Can anyone recommend a tutorial on writing triggers, aside from what's in
the documentation?

Can a trigger in a table in Database_A alter/insert data in a table in
Database_B?

Can I write a trigger such that, it runs on every insert into Table_A, and
inserts a subset of fields of this insert into Table_B, but if this is not
successful, then the insert on Table_A also fails?

Thanks
-Josh

am  06.12.2005, um 10:49:31 -0500 mailte Joshua Kramer folgendes:
>
> Greetings all,
>
> Can anyone recommend a tutorial on writing triggers, aside from what's in
> the documentation?
>
> Can a trigger in a table in Database_A alter/insert data in a table in
> Database_B?

No, you can't. (except with dblink)


>
> Can I write a trigger such that, it runs on every insert into Table_A, and
> inserts a subset of fields of this insert into Table_B, but if this is not
> successful, then the insert on Table_A also fails?

Yes.


HTH, Andreas
--
Andreas Kretschmer    (Kontakt: siehe Header)
Heynitz:  035242/47212,      D1: 0160/7141639
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 ===    Schollglas Unternehmensgruppe    ===

On Tue, Dec 06, 2005 at 05:36:45PM +0100, A. Kretschmer wrote:
> am  06.12.2005, um 10:49:31 -0500 mailte Joshua Kramer folgendes:
> > Can a trigger in a table in Database_A alter/insert data in a table in
> > Database_B?
>
> No, you can't. (except with dblink)

Or with procedural languages like PL/Perl that allow you to do just
about anything you want (connect to another database, send email,
etc.).  However, a drawback is that you don't get transactional
semantics: if you roll back the transaction there's no way to undo
the trigger's actions.

--
Michael Fuhr