Question

I noticed that, for the most part, Django does not enforce default values on the database level.

Field definition in model:

description = models.TextField(default='')

SQL:

description | text   | not null

If I add a row using raw SQL (as described here: https://docs.djangoproject.com/en/dev/topics/db/sql/#executing-custom-sql-directly), and don’t include a value for a field that has a default, will the default still be used?

Answer 1

No.

At least, not based on a test I just did.

models.py:

class Recipient(models.Model):
    mailing = models.ForeignKey(Mailing, related_name="recipients")
    email = models.EmailField()
    how_sent = models.CharField(max_length=1, choices=SENT_TYPES, default="U")
    user = models.ForeignKey(User, blank=True, null=True)
    date_sent = models.DateTimeField(auto_now_add=True)
    date_viewed = models.DateTimeField(null=True, blank=True)

    def __unicode__(self):
        return "%s -> %s (%s)" % (self.mailing, self.email, self.date_sent)

And then I rand this code:

>>> cursor.execute("""insert into mailings_recipient (mailing_id, email) values (3, '[e-mail]');""")
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "path/to/django/db/backends/util.py", line 40, in execute
    return self.cursor.execute(sql, params)
  File "/path/to/django-pyodbc/sql_server/pyodbc/base.py", line 326, in execute
    return self.cursor.execute(sql, params)
IntegrityError: ('23000', "[23000] [FreeTDS][SQL Server]Cannot insert the value NULL into column 'how_sent', table 'database.dbo.mailings_recipient'; column does not allow nulls. INSERT fails. (515) (SQLExecDirectW)")

If Django entered default values for you, it would have sent a value of “U” for how_sent but instead I got an error.

Then if we create a record using Django,

Recipient.objects.create(mailing=Mailing.objects.all()[0], email='[e-mail]') 

this is the corresponding SQL:

SET NOCOUNT ON INSERT INTO [mailings_recipient] ([mailing_id], [email], [how_sent], [user_id], [date_sent], [date_viewed]) VALUES (1, [e-mail], U, None, 2012-09-14 14:48:59, None) 
;SELECT SCOPE_IDENTITY()

So if you are really asking whether default values will be entered for you if you use something like cursor.execute("INSERT INTO...") then the answer is no, it will not set up those default values for you. As you pointed out, Django does not set up the default values for you when creating your database schema, it merely sets up those default values when performing a normal save.