Models:
class Mark(models.Model):
name = models.CharField(max_length=200, verbose_name="Марка", unique=True, null=True)
#...
class Model(models.Model):
mark = models.ForeignKey(Mark, on_delete=models.CASCADE, verbose_name="Марка")
name = models.CharField(max_length=200, verbose_name="Модель", unique=True, null=True)
#...
class Car(models.Model):
vin = models.CharField(max_length=100, null=True)
#...
class Image(models.Model):
car = models.ForeignKey(Car, related_name='images', on_delete=models.CASCADE)
image = models.ImageField(upload_to=get_upload_path, verbose_name="Фото")
#...
How to make the following query in Django ORM without raw:
query = "SELECT c.*, m.name mark_name, JSON_ARRAYAGG(img.image) image FROM incarcatalog_car c \
LEFT JOIN incarcatalog_mark m ON m.id=c.mark_id \
LEFT JOIN incarcatalog_image img ON img.car_id=c.id \
WHERE c.id>%s \
GROUP BY c.id;"
queryset = Car.objects.raw(query, [id])
My problem... I did a left join for the Mark, Model tables, but I don’t know how to connect the car table with the Image table
queryset = Car.objects.select_related("mark", "model").all()
But i don't know how to create realtionship with Image table.
But i don't know how to create realtionship with Image table.
You don't. The query you propose is problematic: it repeats the same data, which results in a lot of bandwidth from the database to the Django server, and also can increase memory usage.
You use .prefetch_related(…)
[Django-doc] to fetch the images:
queryset = Car.objects.select_related('mark', 'model').prefetch_related('images')
this will fetch the images in a second request, and thus you can then for example print the images with:
for item in queryset:
for image in item.images.all():
print(image.image.url)
If the database supports aggregating data as a list, you can use:
from django.contrib.postgres.aggregates import ArrayAgg
queryset = Car.objects.select_related('mark', 'model').annotate(
imgs=ArrayAgg('images__image')
)