---
title: "Hubungan banyak-ke-satu"
version: 3.2
locale: id
source: https://docs.djangoproject.com/id/3.2/topics/db/examples/many_to_one/
canonical: https://djangodocs.dev/id/3.2/topics/db/examples/many_to_one/
---
# Hubungan banyak-ke-satu

Untuk menentukan hubungan many-to-one, gunakan [`ForeignKey`](/id/3.2/ref/models/fields/#django.db.models.ForeignKey):

```
from django.db import models

class Reporter(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)
    email = models.EmailField()

    def __str__(self):
        return "%s %s" % (self.first_name, self.last_name)

class Article(models.Model):
    headline = models.CharField(max_length=100)
    pub_date = models.DateField()
    reporter = models.ForeignKey(Reporter, on_delete=models.CASCADE)

    def __str__(self):
        return self.headline

    class Meta:
        ordering = ['headline']
```

Apa yang mengikuti adalah contoh-contoh dari tindakan yang dapat dilakukan menggunakan fasilitas API Python.

Buat sedikir Reporter:

```pycon
>>> r = Reporter(first_name='John', last_name='Smith', email='john@example.com')
>>> r.save()

>>> r2 = Reporter(first_name='Paul', last_name='Jones', email='paul@example.com')
>>> r2.save()
```

Buat sebuah Artikel:

```pycon
>>> from datetime import date
>>> a = Article(id=None, headline="This is a test", pub_date=date(2005, 7, 27), reporter=r)
>>> a.save()

>>> a.reporter.id
1

>>> a.reporter
<Reporter: John Smith>
```

Catat bahwa anda harus menyimpan sebuah obyek sebelum itu dapat diberikan ke hubungan foreign key. Sebagai contoh, membuat `Article` dengan `Reporter` tidak disimpan memunculkan `ValueError`:

```pycon
>>> r3 = Reporter(first_name='John', last_name='Smith', email='john@example.com')
>>> Article.objects.create(headline="This is a test", pub_date=date(2005, 7, 27), reporter=r3)
Traceback (most recent call last):
...
ValueError: save() prohibited to prevent data loss due to unsaved related object 'reporter'.
```

Obyek artikel mempunyai akses ke obyek Reporter terkait:

```pycon
>>> r = a.reporter
```

Buat sebuah Article melalui obyek Reporter:

```pycon
>>> new_article = r.article_set.create(headline="John's second story", pub_date=date(2005, 7, 29))
>>> new_article
<Article: John's second story>
>>> new_article.reporter
<Reporter: John Smith>
>>> new_article.reporter.id
1
```

Buat sebuah artikel baru:

```pycon
>>> new_article2 = Article.objects.create(headline="Paul's story", pub_date=date(2006, 1, 17), reporter=r)
>>> new_article2.reporter
<Reporter: John Smith>
>>> new_article2.reporter.id
1
>>> r.article_set.all()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
```

Tambah artikel sama ke kumpulan artikel berbeda -  periksa bahwa itu berpindah:

```pycon
>>> r2.article_set.add(new_article2)
>>> new_article2.reporter.id
2
>>> new_article2.reporter
<Reporter: Paul Jones>
```

Menambahkan sebuah obyek dari jenis salah memunculkan TypeError:

```pycon
>>> r.article_set.add(r2)
Traceback (most recent call last):
...
TypeError: 'Article' instance expected, got <Reporter: Paul Jones>

>>> r.article_set.all()
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> r2.article_set.all()
<QuerySet [<Article: Paul's story>]>

>>> r.article_set.count()
2

>>> r2.article_set.count()
1
```

Catat bahwa di contoh terakhir artikel telah dipindahkan dari John ke Paul.

Pengelola terkait mendukung pencarian bidang-bidang juga. API otomatis mengikuti hubungan sejauh anda butuhkan. Gunakan garis bawah ganda untuk memisahkan hubungan. Ini bekerja sebanyak tingkatan yang anda inginkan. Tidak ada batasan. Sebagai contoh:

```pycon
>>> r.article_set.filter(headline__startswith='This')
<QuerySet [<Article: This is a test>]>

# Find all Articles for any Reporter whose first name is "John".
>>> Article.objects.filter(reporter__first_name='John')
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
```

Benar-benar cocok tersirat disini:

```pycon
>>> Article.objects.filter(reporter__first_name='John')
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
```

Permintaan dua kali lebih bidang terkait. Ini menterjemahkan pada sebuah keadaan AND dalam klausa WHERE:

```pycon
>>> Article.objects.filter(reporter__first_name='John', reporter__last_name='Smith')
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
```

Untuk pencarian terkait anda dapat menyediakan sebuah nilai primary key atau lewatkan obyek terkait dengan tegas:

```pycon
>>> Article.objects.filter(reporter__pk=1)
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> Article.objects.filter(reporter=1)
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> Article.objects.filter(reporter=r)
<QuerySet [<Article: John's second story>, <Article: This is a test>]>

>>> Article.objects.filter(reporter__in=[1,2]).distinct()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
>>> Article.objects.filter(reporter__in=[r,r2]).distinct()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
```

Anda dapat juga menggunakan queryset daripada daftar harfiah dari instance:

```pycon
>>> Article.objects.filter(reporter__in=Reporter.objects.filter(first_name='John')).distinct()
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
```

Meminta di arah berlawanan:

```pycon
>>> Reporter.objects.filter(article__pk=1)
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article=1)
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article=a)
<QuerySet [<Reporter: John Smith>]>

>>> Reporter.objects.filter(article__headline__startswith='This')
<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]>
>>> Reporter.objects.filter(article__headline__startswith='This').distinct()
<QuerySet [<Reporter: John Smith>]>
```

Menghitung dalam arah berlawanan bekerja dalam hubungan dengan distinct():

```pycon
>>> Reporter.objects.filter(article__headline__startswith='This').count()
3
>>> Reporter.objects.filter(article__headline__startswith='This').distinct().count()
1
```

Permintaan dapat berputar seperti lingkaran:

```pycon
>>> Reporter.objects.filter(article__reporter__first_name__startswith='John')
<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]>
>>> Reporter.objects.filter(article__reporter__first_name__startswith='John').distinct()
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article__reporter=r).distinct()
<QuerySet [<Reporter: John Smith>]>
```

If you delete a reporter, their articles will be deleted (assuming that the
ForeignKey was defined with [`django.db.models.ForeignKey.on_delete`](/id/3.2/ref/models/fields/#django.db.models.ForeignKey.on_delete) set to
`CASCADE`, which is the default):

```pycon
>>> Article.objects.all()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
>>> Reporter.objects.order_by('first_name')
<QuerySet [<Reporter: John Smith>, <Reporter: Paul Jones>]>
>>> r2.delete()
>>> Article.objects.all()
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> Reporter.objects.order_by('first_name')
<QuerySet [<Reporter: John Smith>]>
```

Anda dapat menghapus menggunakan JOIN di permintaan:

```pycon
>>> Reporter.objects.filter(article__headline__startswith='This').delete()
>>> Reporter.objects.all()
<QuerySet []>
>>> Article.objects.all()
<QuerySet []>
```