Hi Michal,
Thanks for the solution. I tried the solution in a different way:
A.objects.annotate(
max_date_created=Max('b__date_created')).filter(b__date_created=F('max_date_created'),
b__text='ABCD')
Hope the above amounts to the same thing as you have suggested.
Thanks.
On Wednesday,
On Tue, Aug 30, 2016 at 11:46:14PM -0700, Web Architect wrote:
> Hi Erik,
>
> I tried your solution but there are some issues:
>
> .filter(date_created=Max('a__b__date_created')) - this is throwing error
> saying not proper use of group function.
>
> If I remove the above, the result isn't cor
Hi Erik,
I tried your solution but there are some issues:
.filter(date_created=Max('a__b__date_created')) - this is throwing error
saying not proper use of group function.
If I remove the above, the result isn't correct where when I go through
each 'a' in the result, associated latest B.text
Thanks Erik. Will try out the solution you mentioned.
On Tuesday, August 30, 2016 at 3:59:20 PM UTC+5:30, Erik Cederstrand wrote:
>
>
> > Den 30. aug. 2016 kl. 11.20 skrev Erik Cederstrand <
> erik+...@cederstrand.dk >:
> >
> > I'm not even sure that's possible to express in SQL, but it would
>
Maybe this can help you
https://docs.djangoproject.com/en/1.10/topics/db/aggregation/
terça-feira, 30 de Agosto de 2016 às 07:33:14 UTC+1, Web Architect escreveu:
>
> Hi,
>
> I am looking for an elegant and efficient mechanism to have a query filter
> or a solution for the following one to many
> Den 30. aug. 2016 kl. 11.20 skrev Erik Cederstrand
> :
>
> I'm not even sure that's possible to express in SQL, but it would probably be
> quite convoluted if it is. Here's an easier-to-understand solution:
>
> res = set()
> for b in B.objects.all().select_related('a').annotate(Max('date_cre
Hi Erik,
Thanks for the solution.
So, I understand we get all instances of B which are max (date created) or
latest (date created) for each instance of A and then we check b.text ==
'ABCD' and select the corresponding instance of A.
Can't we add additional filter to check if text='ABCD' inste
> for b in B.objects.all().select_related('a').annotate(Max('date_created')):
That should probably be: Max('a__b__date_created') instead.
Erik
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I'm not even sure that's possible to express in SQL, but it would probably be
quite convoluted if it is. Here's an easier-to-understand solution:
res = set()
for b in B.objects.all().select_related('a').annotate(Max('date_created')):
if b.date_created != b.date_created__max:
continue
Hi Mike,
Thanks for your response.
I am aware of chaining filters.
The latest() API in django queryset returns an object and not a queryset.
Hence, I cannot add a filter to it.
I had thought about using chaining filters but couldn't find a way.
On Tuesday, August 30, 2016 at 12:18:56 PM UTC
On 30/08/2016 4:33 PM, Web Architect wrote:
Hi,
I am looking for an elegant and efficient mechanism to have a query
filter or a solution for the following one to many relationship model.
Please note the following is just an illustration of the models - hope
it should provide what I am looking
Hi,
I am looking for an elegant and efficient mechanism to have a query filter
or a solution for the following one to many relationship model. Please note
the following is just an illustration of the models - hope it should
provide what I am looking for:
class A(models.Model):
name = models.C
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