On Tuesday, December 8, 2015 at 5:28:08 PM UTC+2, Michael wrote:
>
> On Tuesday, December 8, 2015 at 1:26:52 AM UTC-6, Anssi Kääriäinen wrote:
>>
>>
>> Come to think of it, we already have a workaround:
>> Book.objects.annotate(author_cnt=RawSQL("(select count(*) from author
>> where author.book_id = book.book_id)").
>>
>
> Yes, you can do a subquery to get the Sum or Count but then you cannot
> "filter": `qs.filter(author_cnt__gt=0)` won't work.
>
> I think it would require the correct "GROUP BY" and "HAVING" clause to be
> able to filter, correct?
>
This one actually does work with filter(). As the count is inside a
subselect, it can be used directly in the WHERE clause without GROUP BY or
HAVING. Using a direct count without a subselect wouldn't work.
- Anssi
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