Django - How can I filter and count related objects of different ids

Question

Model 1:

class Member(models.Model):
    id = models.AutoField(primary_key=True)
    names = models.CharField(max_length=255, blank=True)
    student = models.ForeignKey('School', on_delete=CASCADE, null=True, 
    blank=True)

Model 2:

class School(models.Model):
    id = models.AutoField(primary_key=True)

I want to count the total students who are in different schools.

I tried total_student = Members.filter(school=1+5+8).count()but this is not working. Note: 1, 5 and 8 are the ids of the same type of schools in the school model which different members attend.

Please help me get this right.

you mean {"school_name" : count } like this? if you want total students from all the schools all you have to do is Member count without any filter. — Hemal Patel
– Hemal Patel, Commented Aug 5, 2022 at 4:46

Linh Nguyen · Accepted Answer · 2022-08-05 06:50:31Z

1

Use the __in query filter of Django for filtering on multiple data per column:

total_student = Members.filter(student__in=[1,5,8]).count()

edited Aug 5, 2022 at 6:50

answered Aug 5, 2022 at 5:00

Linh Nguyen

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3 Comments

Benoît Over a year ago

Although the name of the foreign key field is weird (student) the proper filter is student_id__in=(1, 5, 8)

Linh Nguyen Over a year ago

@Benoît thank you for the correction, I changed the field name to student. There no different as the format of the list or tuple because in the document __in accepts multiple types In a given iterable; often a list, tuple, or queryset. Also don't have to specify _id because the default field for foreign key is the id

Eliki Bula Over a year ago

@LinhNguyen thank you so much. Appreciate your great help. It worked well.

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