from django.db import models
class Author(models.Model):
name = models.CharField(max_length=100)
def __str__(self):
return self.name
class Book(models.Model):
BOOK_TYPE_FICTION = 0
BOOK_TYPE_NONFICTION = 1
BOOK_TYPE = (
(BOOK_TYPE_FICTION, 'fiction'),
(BOOK_TYPE_NONFICTION, 'nonfiction'),
)
author = models.ForeignKey(Author, related_name='book_author')
name = models.CharField(max_length=200)
book_type = models.IntegerField(default=BOOK_TYPE_FICTION)
created_at = models.DateField()
def __str__(self):
return '"%s", author: %s' % (self.name, self.author.name)
from datetime import date
from books.models import Author, Book
a0 = Author.objects.create(name='Edgar Allan Poe')
Book.objects.bulk_create([
Book(author=a0, name="The Black Cat", book_type=Book.BOOK_TYPE_FICTION, created_at=date(1843, 8, 19)),
Book(author=a0, name="The Cask of Amontillado", book_type=Book.BOOK_TYPE_NONFICTION, created_at=date(1853, 8, 19)),
Book(author=a0, name="A Descent into the Maelström", book_type=Book.BOOK_TYPE_NONFICTION, created_at=date(1863, 8, 19)),
Book(author=a0, name="The Facts in the Case of M. Valdemar", book_type=Book.BOOK_TYPE_FICTION, created_at=date(1873, 8, 19)),
])
a1 = Author.objects.create(name='Author fiction')
Book.objects.bulk_create([
Book(author=a1, name="1943", book_type=Book.BOOK_TYPE_FICTION, created_at=date(1943, 8, 19)),
Book(author=a1, name="1953", book_type=Book.BOOK_TYPE_FICTION, created_at=date(1953, 8, 19)),
Book(author=a1, name="1963", book_type=Book.BOOK_TYPE_FICTION, created_at=date(1963, 8, 19)),
Book(author=a1, name="1973", book_type=Book.BOOK_TYPE_FICTION, created_at=date(1973, 8, 19)),
])
a2 = Author.objects.create(name='Author non fiction')
Book.objects.bulk_create([
Book(author=a2, name="1943", book_type=Book.BOOK_TYPE_NONFICTION, created_at=date(1943, 8, 19)),
Book(author=a2, name="1953", book_type=Book.BOOK_TYPE_NONFICTION, created_at=date(1953, 8, 19)),
Book(author=a2, name="1963", book_type=Book.BOOK_TYPE_NONFICTION, created_at=date(1963, 8, 19)),
Book(author=a2, name="1973", book_type=Book.BOOK_TYPE_NONFICTION, created_at=date(1973, 8, 19)),
])
from django.db.models import Case, When
ids = Book.objects.filter(book_type=Book.BOOK_TYPE_FICTION).order_by('-created_at').values_list('author', flat=True).distinct()
preserved = Case(*[When(pk=pk, then=pos) for pos, pk in enumerate(ids)])
Author.objects.filter(pk__in=ids).order_by(preserved)
Простой
Средний