I got a field with attribute unique, which was not unique [eg 2-time same value]

python3 manage.py migrate --fake

then

python3 manage.py makemigrations

python3 manage.py migrate

this did the trick

This means a slug should be unique. You may have some data in your model. You need to delete all the data in that model and you need to migrate again.

In this situation, you have two ways to fix the error;

1. You need to delete it from the Django admin site. More often than not, it may give an error when you are trying to open the model.

2. Open command prompt

move to project -> py manage.py shell -> from yourappname.models import modelname -> modelname.objects.delete()

Here if you define a product manager for your model. Then you have to define a delete function. Later you should makemigrate, migrate and continue with the second way

I just met this simiilar error: Django UNIQUE constraint failed. I tried examine the code for very long time, but didn’t solve it. I finally used SQLiteStudio to examine the data, and found the data is problematic: I unintentionally added two SAME instances which violates the UNIQUE constraint. To be frank I haven’t thought the error could be this naive and simple, and because so it took me a lot of time to find out!

I had the same problem and tried all the suggested answers. What finally worked for me was, after I defined the slug field as a URL in models, and ran the makemigrations. I edited the file in makemigrations adding a random number at the end of a basic URL, like this

Generated by Django 3.2.3 on 2022-02-02 20:58

from django.db import migrations, models
from random import randint

class Migration(migrations.Migration):

dependencies = [
    ('blog', '0002_remove_post_slug1'),
]

operations = [
    migrations.AddField(
        model_name='post',
        name='slug',
        field=models.URLField(blank=True, default='http:/salpimientapa.com/' + str(randint(100000,999999))),
    ),
]

After I ran
python manage.py migrate

I edit the slug as a SlugModel and ran the makemigrations and migrate again

What worked for me was going to the admin and changing the value of duplicate slug, before running the migrations again.

Just delete the last migration in the migration folder

Then run

python manage.py makemigrations 
python manage.py migrate

I faced the same issue and solved by populating my slugfied thro’ the admin with unique values and without leaving any of them blank.

Basically: You add the field without unique=true in one operation, make a data migration that generates the correct shortuuids for you, and then change the field too unique again.

i have this error too ,
i did delete my database in djangoProject ( for example db.sqlite3 )
and then run

python manage.py makemigrations

python manage.py migrate

It’s an Integrity Error probably because the migration will temper with the already exiting data in the database.
I had this error and here’s what I did:

• Enter in the project folder directory

• Open the python interpreter

py manage.py shell

• Import your Models

from yourappname.models import model

• Delete existing data records in the model

model.objects.all().delete()

• Exit the Python Interpreter

exit()

.

Another thing you could do is to set unique="false" on the affecting field. I think this should work; not so sure.

Deleting migration is not always the best way! In the event, you wish to maintain your db and want to add unique filed to an existing table. Here is a step to bypass the error and still maintain your db records.

1. Run makemigrations
2. Edited the migration file and removed unique=True (0039_alter_course_options_rename_created_course_timestamp_and_more).

eg:
Before

 migrations.AddField(
        model_name='content',
        name='uuid',
        field=models.UUIDField(default=uuid.uuid4, unique=True),
    ),

After

 migrations.AddField(
        model_name='content',
        name='uuid',
        field=models.UUIDField(default=uuid.uuid4),
    ),

3. Now if you migrate, it should run fine. Next, you need to update all previous records.

Create a custom managements

courses/
├── __init__.py
├── management/
│   ├── __init__.py
│   └── commands/
│       ├── __init__.py
│       └── check_uuid_uniqueness.py
├── models.py
├── ...
└── ...

Mine looks like so in the check_uuid_uniqueness.py

from django.apps import apps
from django.core.management.base import BaseCommand
import uuid

class Command(BaseCommand):
 help = 'Check the uniqueness of uuid fields in models and generate unique values if necessary.'

 def handle(self, *args, **options):
     app_name = 'courses'
     models = apps.get_app_config(app_name).get_models()

     for model in models:
         if hasattr(model, 'uuid'):
             instances = model.objects.all()
             for instance in instances:
                 list_item = instances.filter(uuid=instance.uuid)
                 if not instance.uuid or len(list_item)>1:
                     instance.uuid = uuid.uuid4()
                     instance.save()
                     print(model, ' updated: ', instance.uuid)

     self.stdout.write(self.style.SUCCESS('UUID uniqueness check completed.'))

Remember, in my case, I was targeting uuid, yours could be slug.

4. Finally, run the custom command (make sure your python venv is activated)

python manage.py check_uuid_uniqueness

python manage.py dbshell
>> DROP TABLE rango_category__new.slug;

delete associated migration file;

python manage.py makemigration
python manage.py migrate