如果字段存在，则Django过滤查询集

Question

当且仅当我的模型loan中存在ShgGroupLoanMarking时，我想过滤我的查询集。

class ShgGroupLoanMarking(models.Model):
 shg = models.ForeignKey(Shg, null=True)
 category = models.CharField(max_length=25, choices=GROUP_CATEGORY, default="shg_group")
 msss = models.ForeignKey(Msss, null=True)
 shgmember = models.ForeignKey(ShgMember, null=True)
 loan = models.ForeignKey(Loan, null=True)
 date_of_marking = models.DateField(null=True)
 paid = models.CharField(max_length=100, null=True)
 loan_amount = models.CharField(max_length=100, null=True)
 service_charge = models.CharField(max_length=100, null=True)
 description = models.CharField(max_length=100, null=True)
 status = models.CharField(max_length=100, null=True)
 print_status = models.BooleanField(default=False)
 sent_to_bank_status = models.BooleanField(default=False)
 receipt_number = models.IntegerField(default=0)

怎么做？

Answer 1

ShgGroupLoanMarking.objects.filter(loan__isnull=False)

或

ShgGroupLoanMarking.objects.exclude(loan=None)