It is impossible to add a non-nullable field 'name' to table_name without specifying a default
Question:
I have added a following field in my already existing model:
name = models.CharField(max_length=128, unique=True)
But it is giving following prompt when applying migrations:
It is impossible to add a non-nullable field 'name' to table_name without specifying a default. This is because 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 manually define a default value in models.py.
I cannot set it’s attributes to blank=True, null=True as this field is must. I cannot set it’s default value as the field has to be unique. I also deleted all the previous data from that table.
If I try to set it’s default value in command prompt, it says plz select a valid option.
How to fix it?
Answers:
The issue is that you probably have existing records, but this field is new and unique.
This is what I suggest to do:
- Use
blank=True, null=True
- Fill the existing records with unique names using data migration or manually.
- Remove
blank=True and null=True in next migration
It is impossible to add a non-nullable field ‘name’ to table_name without specifying a default. This is because 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 manually define a default value in models.py.
Solution:
Select option 1) Provide a one-off default now (will be set on all existing rows with a null value for this column) for now and then go to your models and make these changes:
name = models.CharField(max_length=128, blank=True)
Note* : you must remove name(unique = True) because blank names will not be unique and for uniquiness use id as a primary key
I have added a following field in my already existing model:
name = models.CharField(max_length=128, unique=True)
But it is giving following prompt when applying migrations:
It is impossible to add a non-nullable field 'name' to table_name without specifying a default. This is because 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 manually define a default value in models.py.
I cannot set it’s attributes to blank=True, null=True as this field is must. I cannot set it’s default value as the field has to be unique. I also deleted all the previous data from that table.
If I try to set it’s default value in command prompt, it says plz select a valid option.
How to fix it?
The issue is that you probably have existing records, but this field is new and unique.
This is what I suggest to do:
- Use
blank=True,null=True - Fill the existing records with unique names using data migration or manually.
- Remove
blank=Trueandnull=Truein next migration
It is impossible to add a non-nullable field ‘name’ to table_name without specifying a default. This is because 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 manually define a default value in models.py.
Solution:
Select option 1) Provide a one-off default now (will be set on all existing rows with a null value for this column) for now and then go to your models and make these changes:
name = models.CharField(max_length=128, blank=True)
Note* : you must remove name(unique = True) because blank names will not be unique and for uniquiness use id as a primary key