CODEWITHSUNDEEP
pythondjangodjango-modelsdjango-orm
rahnama7m
rahnama7m

Reputation: 977

UNIQUE constraint failed Error when save new obj in django

I have this model: 

#models.py
class Enrollment(models.Model):
    student = models.ForeignKey(User, on_delete=models.PROTECT)
    curriculum = models.ForeignKey(Curriculum, on_delete=models.PROTECT)
    enrolment_date = models.DateTimeField(null=True,blank=True,auto_now_add=True)
    payed_amount = models.PositiveIntegerField(null=True,blank=True)
    is_complete_paid = models.BooleanField(null=True,blank=True,default=False)

    class Meta:
        unique_together = (("student", "curriculum"),)

and when I want to create new enrollment in my views.py with this codes: 

new_enrollment = Enrollment.objects.create(student_id=request.user.id,curriculum_id=curriculum_id)

I got this error:

UNIQUE constraint failed: lms_enrollment.student_id, lms_enrollment.curriculum_id

Why this error happened? Is it possible to explain the cause of this error and introduce some documentations about that?

Upvotes: 1

Views: 1139

Answers (1)

Işık Kaplan
Işık Kaplan

Reputation: 2982

class Enrollment(models.Model):
    student = models.ForeignKey(User, on_delete=models.PROTECT)
    curriculum = models.ForeignKey(Curriculum, on_delete=models.PROTECT)
    payed_amount = models.PositiveIntegerField(null=True, blank=True)

    class Meta:
        unique_together = (("student", "curriculum"),)

Meta.unique_together means that both of the fields can't be same for more than 1 item in the database

Enrollment.objects.create(student=student1, curriculum=curriculum1, payed_amount=100)
Enrollment.objects.create(student=student2, curriculum=curriculum1, payed_amount=200)
#Only curriculum is the same
Enrollment.objects.create(student=student1, curriculum=curriculum2, payed_amount=300)
#Only student is the same
Enrollment.objects.create(student=student1, curriculum=curriculum1, payed_amount=400)
#Both student and curriculum is the same with the first object,
hence it raises UNIQUE constraint failed error

Upvotes: 1

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