django中缺少必需的Charfield的字段被保存为空字符串，并且不会引发错误

Question

If I try to save incomplete model instance in Django 1.10, I would expect Django to raise an error. It does not seem to be the case.

models.py:

from django.db import models

class Essai(models.Model):
    ch1 = models.CharField(max_length=100, blank=False)
    ch2 = models.CharField(max_length=100, blank=False)

So I have two fields not allowed to be empty (default behavior, NOT NULL restriction is applied by Django at MySQL table creation). I expect Django to rase an error if one of the fields is not set before storing.

However, when I create an incomplete instance, the data is stored just fine:

>>> from test.models import Essai
>>> bouh = Essai()
>>> bouh.ch1 = "some content for ch1"
>>> bouh.save()
>>> bouh.id
9
>>> bouh.ch1
'some content for ch1'
>>> bouh.ch2
''
>>> 

I would have expected Django to raise an error. If I force ch2 to None , however, it raises an error:

>>> bouh = Essai()
>>> bouh.ch1 = "some content for ch1"
>>> bouh.ch2 = None
>>> bouh.save()
Traceback (most recent call last):
  (...)
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: NOT NULL constraint failed: test_essai.ch2
>>> bouh.id
>>> bouh.ch1
'some content for ch1'
>>> bouh.ch2
>>>

Is this normal behavior? Did I miss something? Why is Django not raising an error as default behavior in this simple case?

Thanks for your lights!

EDIT

I got a few replies pointing out the fact that in SQL empty string "" is not equivalent to NULL, as stated in Django model blank=False does not work? However, if we look at ModelForm behavior, there seem to be a inconsistency in django doc.

see question Followup : missing required Charfield in django Modelform is saved as empty string and do not raise an error

Answer 1

Use this,

from django.db import models

class Essai(models.Model):
    ch1 = models.CharField(max_length=100)
    ch2 = models.CharField(max_length=100)