Re: Column as result of subtraction of two other columns?

> -----Original Message-----
> From: John Sidney-Woollett [mailto:johnsw@wardbrook.com]
> Sent: 16 July 2004 16:22
> To: Bruno Wolff III
> Cc: Mark Cave-Ayland; pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Column as result of subtraction of two
> other columns?
>
>
> Try
>
> select a, b, (b - a) as diff from (
>   select 1 as a, 2 as b
> ) as tmp;
>
> John Sidney-Woollett


Hi John,

Brilliant - thanks for this! The reason I would like to do it this way
is because in my real database, both a and b are horribly complex with 6
or more joins, and it seems a waste for the database to calculate both
results again just to give the difference. I'll give this a go on Monday
and shout if I still can't get it to work.


Many thanks,

Mark.

---

Mark Cave-Ayland
Webbased Ltd.
Tamar Science Park
Derriford
Plymouth
PL6 8BX
England

Tel: +44 (0)1752 764445
Fax: +44 (0)1752 764446


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