Django聚合:两个字段相乘的总和

问题描述

我有一个类似这样的模型:

I have a model something like this:

class Task(models.Model):
    progress = models.PositiveIntegerField()
    estimated_days = models.PositiveIntegerField()

现在我想在数据库级别进行计算Sum(progress *estimated_days).使用 Django Aggregation 我可以得到每个字段的总和，但不能得到字段乘法的总和.

Now I would like to do a calculation Sum(progress * estimated_days) on the database level. Using Django Aggregation I can have the sum for each field but not the summation of multiplication of fields.

推荐答案

更新: for Django >= 1.8 请按照@kmmbvnr 提供的答案

Update: for Django >= 1.8 please follow the answer provided by @kmmbvnr

可以使用 Django ORM:

it's possible using Django ORM:

这是你应该做的:

from django.db.models import Sum

total = ( Task.objects
            .filter(your-filter-here)
            .aggregate(
                total=Sum('progress', field="progress*estimated_days")
             )['total']
         )

注意:如果两个字段的类型不同，请说 integer &float，要返回的类型应该作为Sum

Note: if the two fields are of different types, say integer & float, the type you want to return should be passed as the first parameter of Sum

这是一个迟到的答案，但我想它会帮助寻找相同的人.

It's a late answer, but I guess it'll help someone looking for the same.

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