Django cannot query data from another table by using OneToOneField

Question

I create django model like this which api_key of Setting table is OneToOneField to Key table.

class Key(models.Model):
    
    api_key=models.CharField(max_length=100,unique=True)
    api_key_name=models.CharField(max_length=100)
    
    def __str__(self):
        return self.api_key

class Setting(models.Model):

    api_key=models.OneToOneField(Key,on_delete=models.CASCADE)
    field_en=models.BooleanField(default=False)

    def __str__(self):
        return str(self.api_key)

I add data to table Key like this.

api_key="abc1"
api_key_name="test"

In views.py I use key to query like this code.

def keyForm(request):

    key="abc1"
    data, created = Setting.objects.get_or_create(api_key__api_key=key)
    key = Key.objects.get(api_key=key)

    data = {'setting':data, 'key':key}

    return render(request,'key_form.html', data)

Data in table Key
It show error like this. How to fix it?

MySQLdb._exceptions.OperationalError: (1048, "Column 'api_key_id' cannot be null")

IntegrityError at /keyForm
(1048, "Column 'api_key_id' cannot be null")

Asked By: user572575

||

Source

Answer 1

Change data, created = Setting.objects.get_or_create(api_key__api_key=key) to data, created = Setting.objects.get_or_create(api_key_id=key). Should work.

But it would be better if you validate key as well:

from django.shortcuts import get_object_or_404

def key_form(request):

    key="abc1"
    key_instance = get_object_or_404(Key, api_key=key)
    data, created = Setting.objects.get_or_create(api_key=key_instance)
    key = Key.objects.get(api_key=key)

    data = {'setting':data, 'key':key}

    return render(request,'key_form.html', data)

Answered By: Zorking

Answer 2

You are linking Settings to DeviceKey, and not to Key

class Setting(models.Model):

    api_key=models.OneToOneField(DeviceKey,on_delete=models.CASCADE)
    field_en=models.BooleanField(default=False)

    def __str__(self):
        return str(self.api_key)

You are getting the error in key_form view, because
when you create a Settings object you are providing key value as a parameter, and in Django it doesn’t work this way. You need to provide a valid key instance, as a parameter.

The code provided by Zorking explains how you can do this.

Answered By: alv2017

Django cannot query data from another table by using OneToOneField

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