我们可以在Django ORM中对CharField求和吗？ [英] Can we do a Sum on CharField in Django ORM?

问题描述

我在Django ORM中的模型是这个

My model in Django ORM is this

class Test(Modelbase):
    id = models.IntegerField(null=True, blank=True)
    amount = models.CharField(max_length=255)

我要为ID列表添加金额。唯一的问题是金额字段是 CharField 。如何在金额字段中应用总和？

I want to add the amount for list of id's. The only problem is the amount field is CharField. How do I apply sum for the amount field?

Test.objects.filter(id__in=[1,2,3]).aggregate(Sum('amount'))

我正在使用 Django = 1.9.1 。

推荐答案

您可以尝试<使用来对code>进行注释从django.db.models投射

you can try do annotate with cast:

from django.db.models import FloatField
from django.db.models.functions import Cast

Test.objects.filter(id__in=[1,2,3]
    ).annotate(as_float=Cast('amount', FloatField())
    ).aggregate(Sum('as_float'))

注意用于Django< ; 1.10，您应该在Cast base /＃Cast rel = noreferrer>源Cast
或

Note for django < 1.10, you should define Cast here the source Cast Or

from django.db.models import Sum, Func, F

Test.objects.annotate(
    num=Func(
        F('amount'),
        template='%(function)s(%(expressions)s AS %(type)s)',
        function='Cast', type='float')
   ).aggregate(Sum('num'))

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