On Tue, 2007-07-17 at 01:59 -0700, jj wrote:
> It's easy to fetch extra object attributes with extra(select={...}).
>
> But how can I obtain extra sub-objects (easily, without resorting to
> custom SQL)?
>
> I'd like to be able to do something like the following, but obviously
> this doesn't work:
> extra(select={'country': 'SELECT book_country.name,
> book_country.code'})
>
> What works is:
> extra(select={'country_name': 'SELECT book_country.name'},
> 'country_code': 'SELECT book_country.code'})
That's the way to do it (or custom SQL). At some point, if you're
wanting to have tight control over the SQL like this, you should expect
to write it directly. There's nothing bad about that. Django doesn't
replace SQL for those who want that control.
Even with the work I'm doing at the moment making query construction
easier with the QuerySet rewrite, a lot of nested queries won't become
too much easier, at least initially, since the nested query depends on
values in the outer query (otherwise you could run it separately, or
could de-nest it) and it's hard to make it easy to pass those
dependencies around without reimplementing SQL, which, again, is not a
very worthwhile exercise.
Regards,
Malcolm
--
The early bird may get the worm, but the second mouse gets the cheese.
http://www.pointy-stick.com/blog/
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