--- In firebird-support@yahoogroups.com, "Martijn Tonies"
<m.tonies@u...> wrote:

> Hi,
> >
> > I have some tables that contain records that the user should not

be

> > able to modify or delete. Other records in the same table

should be

> > freely modified, deleted, whatever. I'm trying to come up with
> > an 'on update or delete' trigger that will prevent the change if

a

> > field value exists.
> >
> > if (NEW.SomeField = 0) then
> > DoNotChangeMe;
> >
> > Is something like this possible from within a trigger or is

there a

> > better way to protect these records at the server level?
>
> You can do this via a trigger that raises an exception...
>
> Here's an example:
> CREATE EXCEPTION DELETE_NOT_ALLOWED 'System data - not allowed to

delete

> this.';
>
>
> SET TERM ^^ ;
> CREATE TRIGGER CATEGORIE_SYSTEEM FOR CATEGORIE ACTIVE BEFORE

DELETE POSITION

> 0 AS
> BEGIN
> if (old.SYSTEEM = 'T')
> then exception DELETE_NOT_ALLOWED;
> END
> ^^
> SET TERM ; ^^
>
> Of course, you DO need to handle the exception :-)

I can see where this would work but I would prefer that the server
just disallow the deletion. I don't want my client application to
have to handle the exception; I just want the record to not be
deleted. Is there another way?

Steve