Django：返回匹配和不匹配的记录

Question

I am trying to implement an OUTER JOIN functionality with existing Django features/commands.

I have this model:

class ClinicDoctor(models.Model):
    doctor = models.ForeignKey('User', related_name='doctorsF') # single quotes (') because User table is defined down the code.
    clinic = models.ForeignKey(Clinic, related_name='clinicsF')

and

class User(AbstractUser):
    clinics = models.ManyToManyField(Clinic, through='ClinicDoctor', related_name='doctors')

I need to get list of all doctors along with their associated clinics. I am able to get the list if they have clinics associated with them. But I am not able to get those doctors who have no clinics linked to them.

I tried this:

doctorsQuerySet = ClinicDoctor.objects.filter(doctor__groups__name='Doctor').distinct()

It doesn't work as it does sort of INNER JOIN

This query will give me all the doctors. But I don't know who to proceed to fetch all doctors irrespective clinic associations.

doctorsQuerySet = User.objects.filter(groups__name='Doctor').order_by('full_name')

I have to show clinics along with doctors, if they have any. It seems to be functionality similar to OUTER JOIN . How do we do it in Django?

Thank you.

Answer 1

If you define doctors as users assigned to the 'Doctor' group, the first query is right:

doctorsQuerySet = User.objects.filter(groups__name='Doctor').order_by('full_name')

By using a loop you can now get over each user and read the data related to the clinics.

for doctor in doctorsQuerySet:
    clinics = doctor.clinics.all()

Since this will cause additional queries on every iteration you should consider to use a prefetch in the query:

doctorsQuerySet = User.objects.filter(groups__name='Doctor').prefetch_related('clinics').order_by('full_name')

Hope this helps :)