IntegrityError：NOT NULL 约束失败：

Question

from django.db import models
from django.contrib.auth.models import User


class TaskList(models.Model):
    manage = models.ForeignKey(User, on_delete=models.CASCADE, default=None)
    task = models.CharField(max_length=300)
    done = models.BooleanField(default=False)

    def __str__(self):
        return self.task + " - " + str(self.done)

I keep getting this error: NOT NULL constraint failed: new__todolist_app_tasklist.manage_id after I "python manage.py migrate".

Any suggestions?

Answer 1

Try to set the ForeignKey to null=True to allow None values, as this is the default you defined.

from django.db import models
from django.contrib.auth.models import User


class TaskList(models.Model):
    manage = models.ForeignKey(User, on_delete=models.CASCADE, null=True, default=None)
    task = models.CharField(max_length=300)
    done = models.BooleanField(default=False)
    # ...

As you are setting on_delete=models.CASCADE , all TaskList of a user will be deleted, if you delete the related User object. If this is the desired behaviour, null=True, default=None should not be necessary and used.

If you like to keep the TaskList even if the User ist deleted, use on_delete=models.SET_NULL , as yopu already having TaskList objects with None values for the manage field.