Django,中间模型中与给定查询集合的字段数 [英] Django, sum of fields in intermediary model with given queryset
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问题描述
class a (models.Model):
#fields
class b(models.Model):
from_a = models.ForeignKey(a)
to_a = models.ForeignKey(a)
count = models.PositiveIntegerField()
现在,我想知道什么是最好的方法计算b的计数总和,其中from_a是某事物。这个似乎是微不足道的,但我无法确定。
解决方案
from django .db.models import Sum
b.objects.filter(from_a__whatever ='something')。aggregate(Sum('count'))
I have 2 models, one of them has many to many relation with itself through other table like this.
class a(models.Model):
# fields
class b(models.Model):
from_a = models.ForeignKey(a)
to_a = models.ForeignKey(a)
count = models.PositiveIntegerField()
Now, what I wonder is, what is the best way of calculating sum of counts in b's where from_a is "something". This one seems trivial, but I can't figure it out.
解决方案
from django.db.models import Sum
b.objects.filter(from_a__whatever='something').aggregate(Sum('count'))
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