Re: Calculated fileds in pg

On Sun, 24 Nov 2002, Jean-Christian Imbeault wrote:

> Is it possible to set up a field during table creation to be a
> "calculated" field, i.e. the value is calculated from other values.
>
> For example:
>
> Table A:
>
> id integer primary key,
> B_id integer references B(id),
> cost integer default 0
>
> Table B:
>
> id integer primary key,
> total integer -- select sum(cost) from A where B_id=id;
>
> If not should I be looking at implementing this with a view or maybe a
> trigger?

I'd probably do B as a view if it was this simple, because writing the
triggers for A sound to be problematic from a getting the concurrency
right without potential deadlocks standpoint.