OnetoOne (primary_key=Tue) to ForeignKey in Django

Question

I have a OnetoOne field with primary_key=True in a model. Now I want to change that to a ForeignKey but cannot since there is no 'id'.

From this:

user = models.OneToOneField(User, primary_key=True, on_delete=models.CASCADE)

To this:

user1 = models.ForeignKey(User, related_name='questionnaire', on_delete=models.CASCADE)

Showing this while makemigrations:

You are trying to add a non-nullable field 'id' to historicaluserquestionnaire 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

So how to do that? Thanks!

What if you try allowing nulls like null=True, or set a default user as default=<have your default user here> — Adil Shirinov
No its the same thing because primary key was True so there was no id to those objects — Harshit verma

Subhasis Patra Subhasis Patra · Accepted Answer · 2020-05-21T08:28:43

just delete your previous migrations

e.g 

    migrations:
          |
          |- 001.initail.py
          |- 002.examplefiles.py

you just have to delete you most recent migrations and

run the command

python3 manage.py makemigrations
python3 manage.py migrate

OnetoOne (primary_key=Tue) to ForeignKey in Django

2 Answers