Re: Trigger

Hi

> twice inside of one transaction (WRT key changes), it's possible to
> fool the trigger and end up with inconsistent data in a multiuser
> environment.

OK let's assume that customer is not deleted while order is
enetered. At my work I have used InterBase quite a lot. Up to IB 5
there was also no foreign keys, so it had to be done with triggers
just like in PostgreSQL. So when using IB 4 I usually did
something like this:

CREATE EXCEPTION CHILD_INSERT_RESTRICT "Cannot
INSERT ORDER because CUSTOMER does not exist in
CUSTOMER table";

CREATE TRIGGER BI_ORDER FOR ORDER BEFORE INSERT
AS

DECLARE VARIABLE numrows INTEGER;
BEGIN
select count(distinct CustomerID)
from customer
where CustomerID=NEW.CustomerID
into numrows;
IF (numrows = 0 ) THEN
BEGIN
EXCEPTION CHILD_INSERT_RESTRICT;
END

END

I think there is some small syntax differences in PostgreSQL.
So, can somebody please put this into PostgreSQL syntax for me?
I searched the manuals but found no Exeption ... is it possible to
use Exceptions in PostgreSQL?
Also, does there excist special aliases like NEW and OLD in
PostgreSQL?

Thanks
Raigo