[Django]-You are trying to add a non-nullable field 'id' to contact_info without a default

you could set `default=”” and also editable=False.

E.g first_name = models.CharField(max_length=50, default="", editable=False).

Adding id field is unnecessary. Django will add it automatically.

Edit: Deleting the last migration files in your migrations folder and retry again. If it doesn’t work, repeat the same process, you will know you have deleted the right file when your “makemigrations” command works.

You need to set a default value. For example:

field_eg = models.CharField(default="")

means:

name = models.CharField(max_length=100, default="")

Check Your Migration Files

./manage.py showmigrations <App Name>

[X] 0001_initial

[X] 0002_auto_20181204_1110

Revert Your Migrations Using

./manage.py migrate <App Name> <migration file name>

Eg: 0001_initial.

Or use zero (for complete migration revert)

./manage.py migrate <App Name> zero

Check Your Migrations

./manage.py showmigrations <App Name>

[ ] 0001_initial

[ ] 0002_auto_20181204_1110

Now delete all revert migrations and migrate again.

./manage.py migrate <App Name>

I ran into similar problem when doing makemigration. I had primary key with name ‘Identity’ and other fields in my models to which I applied makemigrations. Later, I changed primary key name to ‘_id’ and I got this error.

You are trying to add a non-nullable field ‘_id’ to swapidentity without a default; we can’t do that (the database needs something to populate existing rows).

Error is bit misleading, but if you change back ‘_id’ to ‘Identity’ you will not get that error.

How to fix?
Delete migration script generated under migrations package. Or manually change primary key in your generated migration script.

In my opinion, completely deleting the migrations is a lazy and bad idea. I did a snafu similar to @Afiz Momin and was able to dig myself out.

I had the following setup:

1. A base abstract model.
2. Override the id field after creation (bad idea)
3. All other subclasses triggered Django migrations to try to create the ID field from the parent class.

So I would get the following every single time I ran makemigrations:

You are trying to add a non-nullable field 'id' to <tablename> without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
2) Quit, and let me add a default in models.py

But there was a way out.

In my first attempt I would just seed a fake value in and then delete the created id column, but this was obviously unsustainable. But on a whim I did the following:

1. Backup the migrations directory to migrations.orig.
2. Run ./manage.py makemigrations to make all migrations.
3. Inspect the newly-created migrations file 0001-initial.

Chances are the model it’s complaining about (<tablename>) is missing vital info. For me, it was missing the bases argument:

migrations.CreateModel(
    name='<ModelName>',
        fields=[
            ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
            ('some_field', models.IntegerField()),
            # ... other fields ...
        ],
        options={
            'abstract': False,
        },
        bases=(<base_classes>),
    ),

4. Now go back to migrations.orig and search for the the migration where the model is first created. The migration line will look similar to the one above.
5. Once you find the line in migrations.orig, modify it to match the new migration code.
6. Restore your original migrations. Delete migrations and rename migrations.orig to migrations.
7. Just for good measure, run ./manage.py makemigrations and ./manage.py migrate. You should get no error messages anymore!
8. If it complains about another model, follow the same procedure described.

you happen to be generating a relationship between tables, what you have to do is add a field null = True, in one of the fields of the tables that the error message is referring to (class contact_info).

This is happening because you have non-empty database. There must be line which has not been created through Django ORM.

Do the following:
python manage.py shell

from <path_to_your_models> import *
print len(list(contact_info.objects.filter(id = None)))

This way you find out how many such rows are there. If you want to keep them just make migration script with some value that you give it to it.

This can also happen if you made some changes in your models.py and tried migrating afterwards. Happened to me once. Deleting the entire database didn’t help after all. In case the error is arriving after adding a Foreign Key, you cannot provide a default or it might be unsafe to set default as null.

Probably Django still has some of the previous migrations files in your myapp/migrations/ folder. Deleting those files might help.

The database needs something to populate existing rows.
So here you want to define some value for it you can use default=””

 contact_info = models.CharField(default="" ,max_length=15)