Re: Join issue on a maximum value

On Wed, Apr 21, 2004 at 14:29:34 -0400,
Heflin <hhogan(at)tampabay(dot)rr(dot)com> wrote:
>
> So a basic JOIN gets this:
>
> SELECT auction.auction_id, image.image_id, image.image_descr
> FROM auction JOIN image ON auction.auction_id = image.auction_id
> WHERE auction.auction_owner = 'Mabel';
>
> Now the problem: I can't seem to remember how to get only the max value
> for the image_id for each auction_id so that the result set would be:

The postgres specific way of doing this is:
SELECT DISTINCT ON (auction.auction_id)
auction.auction_id, image.image_id, image.image_descr
FROM auction JOIN image ON auction.auction_id = image.auction_id
WHERE auction.auction_owner = 'Mabel'
ORDER BY auction.auction_id, image.image_id DESC
;

The more standard way to do it would be joining auction and image
with a group by and max to get the highest image_id and then joining
that result to image again to get the corresponding description.