Re: Triggers

On Fri, 2002-08-16 at 15:14, Tom Lane wrote:
> Oliver Elphick <olly@lfix.co.uk> writes:
> >> Unfortunately the column is defined as not null so I fear the insert
> >> would fail and the trigger never get called. How can I get around this?
>
> > Surely you can use a BEFORE trigger, can't you?
>
> I think we check constraints (including NOT NULL) before firing
> triggers.

No, I just tried it (in 7.2.1).  The BEFORE trigger successfully
replaced a null, thus satisfying the constraint.

> The simple answer to this is not to use a constraint, but to rely on
> insert and update triggers to substitute for a null (or throw an error)
> in that column.
>
>             regards, tom lane
--
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight, UK
http://www.lfix.co.uk/oliver
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