{"title":"Caidrimh go leor","version":"6.0","locale":"ga","docname":"topics/db/examples/many_to_many","url":"/ga/6.0/topics/db/examples/many_to_many/","canonical":"https://djangodocs.dev/ga/6.0/topics/db/examples/many_to_many/","summary":"Chun caidreamh go leor a shainiú, bain úsáid as: class: ~django.db.models.manyToManyField.","html":"

Caidrimh go leorLink to this heading#

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Chun caidreamh go leor a shainiú, bain úsáid as: class: ~django.db.models.manyToManyField.

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Sa sampla seo, is féidir Airteag a fhoilsiú i rudaí éagsúla Foilseacháin ``, agus tá rudaí ``Airteag iolracha ag Foilsiúcháin:

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Python
from django.db import models\n\n\nclass Publication(models.Model):\n    title = models.CharField(max_length=30)\n\n    class Meta:\n        ordering = ["title"]\n\n    def __str__(self):\n        return self.title\n\n\nclass Article(models.Model):\n    headline = models.CharField(max_length=100)\n    publications = models.ManyToManyField(Publication)\n\n    class Meta:\n        ordering = ["headline"]\n\n    def __str__(self):\n        return self.headline\n
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Seo a leanas samplaí d'oibríochtaí is féidir a dhéanamh ag baint úsáide as na háiseanna API Python.

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Create a few Publication instances:

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Python console
>>> p1 = Publication(title="The Python Journal")\n>>> p1.save()\n>>> p2 = Publication(title="Science News")\n>>> p2.save()\n>>> p3 = Publication(title="Science Weekly")\n>>> p3.save()\n
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Cruthaigh Airteag:

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Python console
>>> a1 = Article(headline="Django lets you build web apps easily")\n
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Ní féidir leat é a cheangal le ``Foilsiúcháin ``go dtí go sábhálfar é:

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Python console
>>> a1.publications.add(p1)\nTraceback (most recent call last):\n...\nValueError: "<Article: Django lets you build web apps easily>" needs to have a value for field "id" before this many-to-many relationship can be used.\n
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Sábháil é!

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Python console
>>> a1.save()\n
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Comhcheangail an Airteag le Foilseachán `:

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Python console
>>> a1.publications.add(p1)\n
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Create another Article, and set it to appear in its publications:

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Python console
>>> a2 = Article(headline="NASA uses Python")\n>>> a2.save()\n>>> a2.publications.add(p1, p2)\n>>> a2.publications.add(p3)\n
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Tá sé ceart go leor an dara huair a chur leis, ní dhúbailfidh sé an gaol:

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Python console
>>> a2.publications.add(p3)\n
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Ardaíonn réad den chineál mícheart leis: exc: TypeError:

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Python console
>>> a2.publications.add(a1)\nTraceback (most recent call last):\n...\nTypeError: 'Publication' instance expected\n
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Cruthaigh agus cuir Foilseachán le Airteag` i gcéim amháin ag baint úsáid:meth: ~Django.db.Models.Fields.Related.RelatedManager.Create:

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Python console
>>> new_publication = a2.publications.create(title="Highlights for Children")\n
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Tá rochtain ag rudaí Airteag ar a gcuid rudaí gaolmhara ``Foilsiúcháin ``:

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Python console
>>> a1.publications.all()\n<QuerySet [<Publication: The Python Journal>]>\n>>> a2.publications.all()\n<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>\n
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Tá rochtain ag rudaí Foilseacha ar a gcuid rudaí gaolmhara Airteag:

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Python console
>>> p2.article_set.all()\n<QuerySet [<Article: NASA uses Python>]>\n>>> p1.article_set.all()\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n>>> Publication.objects.get(id=4).article_set.all()\n<QuerySet [<Article: NASA uses Python>]>\n
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<lookups-that-span-relationships>Is féidir caidrimh go leor a cheistiú ag baint úsáidea:ref: `cuardaigh thar fud caidrimh `:

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Python console
>>> Article.objects.filter(publications__id=1)\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n>>> Article.objects.filter(publications__pk=1)\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n>>> Article.objects.filter(publications=1)\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n>>> Article.objects.filter(publications=p1)\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n\n>>> Article.objects.filter(publications__title__startswith="Science")\n<QuerySet [<Article: NASA uses Python>, <Article: NASA uses Python>]>\n\n>>> Article.objects.filter(publications__title__startswith="Science").distinct()\n<QuerySet [<Article: NASA uses Python>]>\n
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Féachann an fheidhm: Meth: ~django.db.models.query.queryset.count: meth: ~django.db.models.query.queryset.Distinct chomh maith:

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Python console
>>> Article.objects.filter(publications__title__startswith="Science").count()\n2\n\n>>> Article.objects.filter(publications__title__startswith="Science").distinct().count()\n1\n\n>>> Article.objects.filter(publications__in=[1, 2]).distinct()\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n>>> Article.objects.filter(publications__in=[p1, p2]).distinct()\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA uses Python>]>\n
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Tacaítear le ceisteanna m2m ar ais (ie, ag tosú ag an tábla nach bhfuil a:class: ~django.db.models.manyToManyField):

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Python console
>>> Publication.objects.filter(id=1)\n<QuerySet [<Publication: The Python Journal>]>\n>>> Publication.objects.filter(pk=1)\n<QuerySet [<Publication: The Python Journal>]>\n\n>>> Publication.objects.filter(article__headline__startswith="NASA")\n<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>\n\n>>> Publication.objects.filter(article__id=1)\n<QuerySet [<Publication: The Python Journal>]>\n>>> Publication.objects.filter(article__pk=1)\n<QuerySet [<Publication: The Python Journal>]>\n>>> Publication.objects.filter(article=1)\n<QuerySet [<Publication: The Python Journal>]>\n>>> Publication.objects.filter(article=a1)\n<QuerySet [<Publication: The Python Journal>]>\n\n>>> Publication.objects.filter(article__in=[1, 2]).distinct()\n<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>\n>>> Publication.objects.filter(article__in=[a1, a2]).distinct()\n<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>\n
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Oibríonn mír gaolmhar a eisiamh mar a bheadh ag súil leat freisin (cé go bhfuil an SQL atá i gceist beagán casta):

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Python console
>>> Article.objects.exclude(publications=p2)\n<QuerySet [<Article: Django lets you build web apps easily>]>\n
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If we delete a Publication, its related Article instances won't be able\nto access it:

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Python console
>>> p1.delete()\n>>> Publication.objects.all()\n<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>]>\n>>> a1 = Article.objects.get(pk=1)\n>>> a1.publications.all()\n<QuerySet []>\n
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If we delete an Article, its related Publication instances won't be\nable to access it:

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Python console
>>> a2.delete()\n>>> Article.objects.all()\n<QuerySet [<Article: Django lets you build web apps easily>]>\n>>> p2.article_set.all()\n<QuerySet []>\n
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Ag cur leis trí fhoirceann 'eile' m2m:

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Python console
>>> a4 = Article(headline="NASA finds intelligent life on Earth")\n>>> a4.save()\n>>> p2.article_set.add(a4)\n>>> p2.article_set.all()\n<QuerySet [<Article: NASA finds intelligent life on Earth>]>\n>>> a4.publications.all()\n<QuerySet [<Publication: Science News>]>\n
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Ag cur leis an gceann eile ag úsáid eochairfhocail:

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Python console
>>> new_article = p2.article_set.create(headline="Oxygen-free diet works wonders")\n>>> p2.article_set.all()\n<QuerySet [<Article: NASA finds intelligent life on Earth>, <Article: Oxygen-free diet works wonders>]>\n>>> a5 = p2.article_set.all()[1]\n>>> a5.publications.all()\n<QuerySet [<Publication: Science News>]>\n
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“Foilseachán” a bhaint as Airteag:

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Python console
>>> a4.publications.remove(p2)\n>>> p2.article_set.all()\n<QuerySet [<Article: Oxygen-free diet works wonders>]>\n>>> a4.publications.all()\n<QuerySet []>\n
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Agus ón gceann eile:

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Python console
>>> p2.article_set.remove(a5)\n>>> p2.article_set.all()\n<QuerySet []>\n>>> a5.publications.all()\n<QuerySet []>\n
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Is féidir tacair chaidrimh a shocrú:

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Python console
>>> a4.publications.all()\n<QuerySet [<Publication: Science News>]>\n>>> a4.publications.set([p3])\n>>> a4.publications.all()\n<QuerySet [<Publication: Science Weekly>]>\n
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Is féidir tacair chaidrimh a ghlanadh:

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Python console
>>> p2.article_set.clear()\n>>> p2.article_set.all()\n<QuerySet []>\n
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Agus is féidir leat a ghlanadh ón gceann eile:

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Python console
>>> p2.article_set.add(a4, a5)\n>>> p2.article_set.all()\n<QuerySet [<Article: NASA finds intelligent life on Earth>, <Article: Oxygen-free diet works wonders>]>\n>>> a4.publications.all()\n<QuerySet [<Publication: Science News>, <Publication: Science Weekly>]>\n>>> a4.publications.clear()\n>>> a4.publications.all()\n<QuerySet []>\n>>> p2.article_set.all()\n<QuerySet [<Article: Oxygen-free diet works wonders>]>\n
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Athchruthaigh an Airteag agus Foilsiúna atá scriosta againn:

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Python console
>>> p1 = Publication(title="The Python Journal")\n>>> p1.save()\n>>> a2 = Article(headline="NASA uses Python")\n>>> a2.save()\n>>> a2.publications.add(p1, p2, p3)\n
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Bulk delete some Publication instances, and the references to deleted\npublications will no longer be included in the related entries:

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Python console
>>> Publication.objects.filter(title__startswith="Science").delete()\n>>> Publication.objects.all()\n<QuerySet [<Publication: Highlights for Children>, <Publication: The Python Journal>]>\n>>> Article.objects.all()\n<QuerySet [<Article: Django lets you build web apps easily>, <Article: NASA finds intelligent life on Earth>, <Article: NASA uses Python>, <Article: Oxygen-free diet works wonders>]>\n>>> a2.publications.all()\n<QuerySet [<Publication: The Python Journal>]>\n
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Scrios mórchóir roinnt alt - ba chóir tagairtí do rudaí scriosta dul:

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Python console
>>> q = Article.objects.filter(headline__startswith="Django")\n>>> print(q)\n<QuerySet [<Article: Django lets you build web apps easily>]>\n>>> q.delete()\n
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Tar éis an: meth: ~django.db.models.query.queryset.delete, ní mór taisce an:class: ~django.db.models.queryset a ghlanadh, agus ba chóir na rudaí tagartha a bheith imithe:

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Python console
>>> print(q)\n<QuerySet []>\n>>> p1.article_set.all()\n<QuerySet [<Article: NASA uses Python>]>\n
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