在模型字段之间进行简单算术的Django查询，并与另一个模型的字段进行比较 [英] Django query with simple arithmetic among model fields and comparison with field from another model

问题描述

（下面的所有代码都是实际代码的简化表示）。

(All code below is a simplified representation of the actual code).

如果我具有以下Django模型：-

If I have the following Django models: -

class Material(models.Model):
    name = models.CharField(max_length=110)

class OrderDetail(models.Model):
    material = models.ForeignKey(Material)
    order_quantity = models.IntegerField()
    quantity_delivered = models.IntegerField(null=True, blank=True)
    is_open = models.BooleanField()
    is_active = models.BooleanField()

class MaterialRequirement(models.Model):
    material = models.ForeignKey(Material)
    quantity = models.IntegerField()

我有一个 MaterialRequirement 模型，我们称之为 material_requirement 。我尝试检索满足以下条件的 OrderDetail 对象：-

I have with me an instance of the MaterialRequirement model, let's call it material_requirement. I am trying to retrieve OrderDetail objects which satisfy the following criteria:-

1. material = material_requirement.material

2. is_open = True

3. is_active = True

4. order_quantity > quantity_delivered

5. material_requirement.quantity <= order_quantity - quantity_delivered

我的问题是如何在下面的ORM查询中合并第5个选择条件。

My question is how do I incorporate the 5th selection criteria in my ORM query below.

order_details = OrderDetail.objects.select_related('material').filter(material=material_requirement.material,
                                                                    is_open=True,
                                                                    is_active=True,
                                                                    order_quantity__gt=F('quantity_delivered'))

推荐答案

order_details = (OrderDetail.objects.select_related('material')
                 .filter(material=material_requirement.material,
                         is_open=True,
                         is_active=True,
                         order_quantity__gt=F('quantity_delivered'),
                         quantity_delivered__gte=F('order_quantity') - material_requirement.quantity,
                         )
)

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