Re: left join + case - how is it processed? - Mailing list pgsql-performance

On Sun, Jan 18, 2009 at 7:30 PM, Chris <dmagick@gmail.com> wrote:

> I have a view that looks like this:
>
>  SELECT
>        CASE
>            WHEN r.assetid IS NULL THEN p.assetid
>            ELSE r.assetid
>        END AS assetid,
>        CASE
>            WHEN r.userid IS NULL THEN p.userid
>            ELSE r.userid
>        END AS userid, p.permission, p."granted", p.cascades
>   FROM sq_ast_perm p
>   LEFT JOIN sq_vw_ast_role r ON r.roleid::text = p.userid::text AND
> r.assetid::text = p.assetid::text;

The effect that you are trying to achieve with CASE statements is
better suited to the COALESCE(...) function.
http://www.postgresql.org/docs/8.3/interactive/functions-conditional.html#AEN14484

--
Regards,
Richard Broersma Jr.

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