CODEWITHSUNDEEP
djangodjango-models
Pradeep Agnihotri
Pradeep Agnihotri

Reputation: 371

ForeignKey Reverse relation query

class Book(models.Model):
    title = models.CharField(max_length=100)
    authors = models.ManyToManyField(Author)
    publisher = models.ForeignKey(Publisher)
    publication_date = models.DateField()

    def __unicode__(self):
        return self.title

i want to get all Publishers who has published at least one book.

Upvotes: 0

Views: 32

Answers (1)

Kevin Christopher Henry
Kevin Christopher Henry

Reputation: 48952

Publisher.objects.filter(book__isnull=False).distinct()

This does a JOIN between the two tables and returns the rows where a book exists. distinct() is used to get rid of duplicate Publishers.

Upvotes: 1

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