Yes, that's the query i'd like to have. On Monday, November 10, 2014 10:38:41 PM UTC-7, Curtis Maloney wrote: > > Can you provide the "natural" SQL version you'd rather see generated? > > Something like: > > SELECT ... FROM myapp_a WHERE NOT EXISTS (SELECT 1 FROM myapp_b T1 WHERE > T1.a_id = myapp_a.id AND T1.criteria = True) > > perhaps? > > > On 11 November 2014 16:18, George Ma <george...@gmail.com <javascript:>> > wrote: > >> Yes, the actual sql is very close to this one. But I just feel this >> approach is like a hack. Because I always have to reverse the logic first >> and then reverse again. Not as natural as exists subquery. >> >> On Monday, November 10, 2014 5:53:47 PM UTC-7, Curtis Maloney wrote: >>> >>> If you want to know the SQL generated for any particular queryset, you >>> can just: >>> >>> print str(qs.query) >>> >>> On 11 November 2014 11:39, George Ma <george...@gmail.com> wrote: >>> >>>> For simplicity, let's assume we have a model A and model B. >>>> >>>> class A(models.Model): >>>> name = models.CharField(max_length=200) >>>> >>>> class B(models.Model): >>>> a = models.ForeignKey(A) >>>> criteria = models.BooleanField(default = False) >>>> >>>> Let's say there's a requirement to find A that doesn't have a B with a >>>> true criteria. To me, it makes more sense to use a "not exists" subquery. >>>> Right now, I have to find all the A with the reverse conditions and >>>> exclude >>>> such cases. Something like: >>>> >>>> A.objects.exclude(pk__in = A.objects.filter(b__criteria = True)) >>>> >>> >>> I think you'll find this would be something like: >>> >>> SELECT .... FROM myapp_a WHERE NOT pk IN (SELECT id FROM myapp_a T1 >>> INNER JOIN myapp_b T2 ON (T1.id = T2.a_id) WHERE T2.criteria = True) >>> >>> The problem with this approach is that: first I don't know how the >>>> performance would be; second, it's not very natural from sql query's >>>> perspective. >>>> >>> >>> Performance should be ok, from what I can see... >>> >>> Would be interested to see what the actual SQL is. >>> >>> -- >>> Curtis >>> >>> -- >> You received this message because you are subscribed to the Google Groups >> "Django developers (Contributions to Django itself)" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to django-develop...@googlegroups.com <javascript:>. >> To post to this group, send email to django-d...@googlegroups.com >> <javascript:>. >> Visit this group at http://groups.google.com/group/django-developers. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-developers/19f716f4-2367-492c-ac1e-a4f48c4a2c01%40googlegroups.com >> >> <https://groups.google.com/d/msgid/django-developers/19f716f4-2367-492c-ac1e-a4f48c4a2c01%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> >> For more options, visit https://groups.google.com/d/optout. >> > >
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