如何定义外键关系？

Question

I'm new to django and the database concepts.

I'm getting the 1042 error code when I'm trying to register student via frontend and don't know where my mistake is

if anyone can help that'd be great.

I tried different ways but none was beneficial.

I can add the student via the admin panel of django but cannot do the same via frontend.

models.py

class Session(models.Model):
    session = models.CharField(max_length=150, default=" ")
    def __str__(self):
        return self.session
    
    def get_absolute_url(self):
        return reverse('datapage')
    
    
class Student(models.Model):
    user = models.OneToOneField(User, on_delete = models.CASCADE, primary_key = True)
    phone_number = models.CharField(max_length=20, blank = True)
    semester = models.CharField(max_length=20, blank = True)
    session_year = models.ForeignKey(Session, on_delete = models.CASCADE)
    
    def __str__(self):
        return str(self.user)

forms.py

session_years = Session.objects.all()
session_year_list = []
for session_year in session_years:
    single_session_year = (session_year.id, session_year.session)
    session_year_list.append(single_session_year)

class StudentSignUpForm(UserCreationForm):
    first_name = forms.CharField(required=True)
    last_name = forms.CharField(required=True)
    email = forms.EmailField(required=True)
    username = forms.CharField(required=True)
    phone_number = forms.CharField(required=True)
    semester = forms.CharField(required=True)
    
    def clean_email(self):
        email = self.cleaned_data.get('email')
        email = email.lower()
        if User.objects.filter(email__iexact=email).exists():
            raise forms.ValidationError('A user has already registered using this email')
        return email
    
    def clean_username(self):
        username = self.cleaned_data.get('username')
        if User.objects.filter(email__iexact=username).exists():
            raise forms.ValidationError('A user has already registered using this username')
        return username
    
    class Meta(UserCreationForm.Meta):
        model = User
        fields = ['first_name', 'last_name', 'email', 'username']
        

    @transaction.atomic
    def save(self):
        user = super().save(commit=False)
        user.is_student = True
        user.first_name = self.cleaned_data.get('first_name')
        user.last_name = self.cleaned_data.get('last_name')
        user.email = self.cleaned_data.get('email')
        user.username = self.cleaned_data.get('username')
        user.save()
        student = Student.objects.create(user=user)
        student.phone_number=self.cleaned_data.get('phone_number')
        student.semester=self.cleaned_data.get('semester')
        student.session_year=self.cleaned_data.get('session_year')
        student.save()
        return user

views.py

class StudentRegister(LoggedInRedirectMixin, CreateView):
    model = User
    form_class = StudentSignUpForm
    template_name = 'registration/user_register.html'

    def form_valid(self, form_class):
        user = form_class.save()
        return redirect('datapage')

Answer 1

@Vatsai Vohera - Correct me if I am wrong.

 session = Session.objects.get(session=self.cleaned_data.get('session_year')
    student.session_year = session

    

Answer 2

You are adding your requested data into session_year field which is not working rather you have to save your requested data to your model Session field session. I hope this will work for you.

Answer 3

You can use related_name='...' field in your ForeignKey attribute and also add this:

session_year = models.ForeignKey(Session,related_name='some thing', on_delete = models.CASCADE, null = True)

then you have to call session_year by related name