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Modelos y ORM ​

El ORM de Django permite definir modelos, relaciones, consultas y migraciones.

Modelo ​

python
class Product(models.Model):
    name = models.CharField(max_length=120)
    sku = models.CharField(max_length=80, unique=True)
    price = models.DecimalField(max_digits=12, decimal_places=2)
    stock = models.PositiveIntegerField(default=0)

Migraciones ​

bash
python manage.py makemigrations
python manage.py migrate

Consultas ​

python
Product.objects.filter(stock__gt=0).order_by("name")

Relaciones ​

python
class Order(models.Model):
    customer = models.ForeignKey(Customer, on_delete=models.PROTECT)
    created_at = models.DateTimeField(auto_now_add=True)
python
Order.objects.select_related("customer")
Product.objects.prefetch_related("categories")

Evitan N+1 queries.

Buenas practicas ​

  • Modela constraints.
  • Usa migraciones.
  • Evita queries en bucles.
  • Revisa SQL con queryset.query.
  • Usa DecimalField para dinero.