convert SQL create query to Django Model

Question

I'm specifically having a problem with the following lines:

`created_at` datetime(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6),
`updated_at` datetime(6) DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP(6),

Here is the full SQL query:

CREATE TABLE `billing_package` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(200) NOT NULL,
  `start` datetime(6) NOT NULL,
  `expiry` datetime(6) DEFAULT NULL,
  `price` decimal(10,2) NOT NULL,
  `count` int(11) DEFAULT NULL,
  `created_at` datetime(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6),
  `updated_at` datetime(6) DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP(6),
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Django Model

class Package(models.Model):

    name = models.CharField(max_length=200, null=False)
    price = models.CharField(max_length=200, null=False)
    start = models.DateTimeField()
    expiry = models.DateTimeField(null=True)
    price= models.DecimalField(max_digits=10, decimal_places=2)
    count = models.IntegerField(null=True, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.user

After running migrations with Django, when i check the database, there is no default value for created_at and updated_at? How do i correctly do the following in a Django Model?

   `created_at` datetime(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6),
   `updated_at` datetime(6) DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP(6),

The defaults are done by Django, not by the database.

willeM_ Van Onsem
– willeM_ Van Onsem

2021-09-13 17:01:50 +00:00
Commented Sep 13, 2021 at 17:01 — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Sep 13, 2021 at 17:01

willeM_ Van Onsem · Accepted Answer · 2021-09-13 17:15:00Z

How do I correctly do the following in a Django Model?

You don't. Django does the processing to obtain a default value. It will thus not set a default in the database model, but Django's ORM will update the fields accordingly.

You can however implement this by making a raw query in a migration file. You can create an empty migration file with:

python manage.py makemigrations --empty app_name

This will create a new file in the migrations directory of app_name. Next you you can write a raw SQL query by altering the file to look like:

# Generated by Django A.B on YYYY-MM-DD HH:MM
from django.db import migrations

class Migration(migrations.Migration):

    dependencies = [
        ('app_name', '0123_some_name'),
    ]

    operations = [
        migrations.RunSQL('ALTER TABLE table_name ALTER created_at SET DEFAULT CURRENT_TIMESTAMP(6)'),
        migrations.RunSQL('ALTER TABLE table_name MODIFY updated_at datetime(6) NULL DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP(6)')
    ]

This will update the database, although it can be different if you use another SQL dialect.

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