Works like a charm.
Thanks!
Ciao
Enrico
On Feb 21, 11:06 pm, Michael Elkins <m...@sigpipe.org> wrote:
> On Tue, Feb 21, 2012 at 01:10:28PM -0800, Enrico wrote:
> >But your query counts all the books, even the bad ones. I only need to
> >count the good ones...
>
> >For example, if my books are:
>
> >1. name: LOTR, rating: 10, publisher: A ...
> >2. name: ASOIAF, rating: 10, publisher: A ...
> >3. name: Twilight, rating 1, publisher: B ...
>
> >and my publishers are:
> >A and B
>
> >Your query returns:
> >[A, num_book=2]
> >[B, num_book=1]
>
> >the query on my first message returns:
> >[A, num_book=2]
>
> >and what I need is:
> >[A, num_book=2]
> >[B, num_book=0]
>
> >where num_books means number of good books.
>
> Sorry, I missed that detail in your question. You need to use the
> .extra() queryset method to do what you are attempting. The
> following will add a 'num_good_books' attribute to each Publisher
> object:
>
> qs = Publisher.objects.extra(select={'num_good_books': 'select count(*) from
> publisher_book where publisher_book.publisher_id = publisher_publisher.id and
> publisher_book.rating > 3.0'})
> for o in qs:
> print o.name, o.num_good_books
>
> Note that the "publisher_" prefix in the SQL is the name of the
> Django application in which your models reside. So if your Django
> application is named "myapp", then you'd need to change the
> "publisher_" prefix to "myapp_".
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