如何查询关联至Invoice或DamageClaim的BillingNumbering数据集？

模型定义 #

class BillingNumbering(models.Model):
    number = models.IntegerField()
    date = models.DateField(default=now)

class Invoice(models.Model):
    number = models.OneToOneField(BillingNumbering, on_delete=models.PROTECT)
    created_at = models.DateTimeField(auto_now_add=True,
                                      null=True, blank=True)

class DamageClaim(models.Model):
    number = models.OneToOneField(BillingNumbering, on_delete=models.PROTECT)
    created_at = models.DateTimeField(auto_now_add=True,
                                      null=True, blank=True)

查询需求 #

需要筛选出仅关联至Invoice或DamageClaim的BillingNumbering对象：

• <BillingNumbering: 1> 关联至Invoice
• <BillingNumbering: 2> 关联至DamageClaim
• <BillingNumbering: 3> 未关联任何模型，访问instance.invoice或instance.damageclaim会触发ObjectDoesNotExist错误

目标是通过BillingNumbering的filter方法，仅返回<BillingNumbering: 1>和<BillingNumbering: 2>。

解决方案 #

参考思路后，最终实现代码如下：

from django.db.models import Q

qs = BillingNumbering.objects.filter(Q(damageclaim__isnull=False) | Q(invoice__isnull=False))

内容的提问来源于stack exchange，提问作者Dean Christian Armada