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

Caidrimh go leor le duineLink to this heading#

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Chun caidreamh go leor le duine a shainiú, bain úsáid as: class: ~django.db.Models.ForeignKey.

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Sa sampla seo, is féidir le Tuairiseoir a bheith bainteach le go leor rudaí Airteag, ach ní féidir ach réad Tuairiscitheoir amháin a bheith ag ``Airteag:

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Code
from django.db import models\n\n\nclass Reporter(models.Model):\n    first_name = models.CharField(max_length=30)\n    last_name = models.CharField(max_length=30)\n    email = models.EmailField()\n\n    def __str__(self):\n        return f"{self.first_name} {self.last_name}"\n\n\nclass Article(models.Model):\n    headline = models.CharField(max_length=100)\n    pub_date = models.DateField()\n    reporter = models.ForeignKey(Reporter, on_delete=models.CASCADE)\n\n    def __str__(self):\n        return self.headline\n\n    class Meta:\n        ordering = ["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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Cruthaigh cúpla Tuairisceoir:

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Python console
>>> r = Reporter(first_name="John", last_name="Smith", email="john@example.com")\n>>> r.save()\n\n>>> r2 = Reporter(first_name="Paul", last_name="Jones", email="paul@example.com")\n>>> r2.save()\n
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Cruthaigh Airteagal:

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Python console
>>> from datetime import date\n>>> a = Article(id=None, headline="This is a test", pub_date=date(2005, 7, 27), reporter=r)\n>>> a.save()\n\n>>> a.reporter.id\n1\n\n>>> a.reporter\n<Reporter: John Smith>\n
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Tabhair faoi deara go gcaithfidh tú réad a shábháil sula bhféadfar é a shannadh do phríomhchaidreamh eachtrach. Mar shampla, ardaíonn Airteag a chruthú le Tuairiseoir neamhshábháilte `Error lua:

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Python console
>>> r3 = Reporter(first_name="John", last_name="Smith", email="john@example.com")\n>>> Article.objects.create(\n...     headline="This is a test", pub_date=date(2005, 7, 27), reporter=r3\n... )\nTraceback (most recent call last):\n...\nValueError: save() prohibited to prevent data loss due to unsaved related object 'reporter'.\n
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Tá rochtain ag rudaí Airteagail ar a gcuid rudaí Tuairisceora

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Python console
>>> r = a.reporter\n
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Cruthaigh Airteagal tríd an réad Tuairisceora:

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Python console
>>> new_article = r.article_set.create(\n...     headline="John's second story", pub_date=date(2005, 7, 29)\n... )\n>>> new_article\n<Article: John's second story>\n>>> new_article.reporter\n<Reporter: John Smith>\n>>> new_article.reporter.id\n1\n
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Cruthaigh alt nua:

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Python console
>>> new_article2 = Article.objects.create(\n...     headline="Paul's story", pub_date=date(2006, 1, 17), reporter=r\n... )\n>>> new_article2.reporter\n<Reporter: John Smith>\n>>> new_article2.reporter.id\n1\n>>> r.article_set.all()\n<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>\n
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Cuir an t-alt céanna le tacar alt difriúil - seiceáil go mbogann sé:

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Python console
>>> r2.article_set.add(new_article2)\n>>> new_article2.reporter.id\n2\n>>> new_article2.reporter\n<Reporter: Paul Jones>\n
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Ardaíonn réad den chineál mícheart a chur leis TypeError:

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Python console
>>> r.article_set.add(r2)\nTraceback (most recent call last):\n...\nTypeError: 'Article' instance expected, got <Reporter: Paul Jones>\n\n>>> r.article_set.all()\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n>>> r2.article_set.all()\n<QuerySet [<Article: Paul's story>]>\n\n>>> r.article_set.count()\n2\n\n>>> r2.article_set.count()\n1\n
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Tabhair faoi deara go bhfuil an t-alt bogadh ó Eoin go Pól sa sampla deireanach.

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Tacaíonn bainisteoirí gaolmhara le cuardach allamuigh freisin. Leanann an API caidrimh go huathoibríoch chomh fada agus is gá duit. Úsáid béim dúbailte chun caidrimh a scaradh. Oibríonn sé seo an oiread leibhéil domhain agus is mian leat. Níl aon teorainn ann. Mar shampla:

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Python console
>>> r.article_set.filter(headline__startswith="This")\n<QuerySet [<Article: This is a test>]>\n\n# Find all Articles for any Reporter whose first name is "John".\n>>> Article.objects.filter(reporter__first_name="John")\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n
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Tá meaitseáil cruinn intuigthe anseo:

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Python console
>>> Article.objects.filter(reporter__first_name="John")\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n
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Fiosrú faoi dhó thar an réimse gaolmhar. Aistríonn sé seo go coinníoll AND sa chlásal WHERE:

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Python console
>>> Article.objects.filter(reporter__first_name="John", reporter__last_name="Smith")\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n
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Maidir leis an gcuardach gaolmhar is féidir leat príomhluach a sholáthar nó an réad gaolmhar a rith go sainráite:

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Python console
>>> Article.objects.filter(reporter__pk=1)\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n>>> Article.objects.filter(reporter=1)\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n>>> Article.objects.filter(reporter=r)\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n\n>>> Article.objects.filter(reporter__in=[1, 2]).distinct()\n<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>\n>>> Article.objects.filter(reporter__in=[r, r2]).distinct()\n<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>\n
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Is féidir leat tacar fiosrúcháin a úsáid freisin in ionad liosta liteartha cásanna:

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Python console
>>> Article.objects.filter(\n...     reporter__in=Reporter.objects.filter(first_name="John")\n... ).distinct()\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n
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Ag fiosrú sa treo eile:

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Python console
>>> Reporter.objects.filter(article__pk=1)\n<QuerySet [<Reporter: John Smith>]>\n>>> Reporter.objects.filter(article=1)\n<QuerySet [<Reporter: John Smith>]>\n>>> Reporter.objects.filter(article=a)\n<QuerySet [<Reporter: John Smith>]>\n\n>>> Reporter.objects.filter(article__headline__startswith="This")\n<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]>\n>>> Reporter.objects.filter(article__headline__startswith="This").distinct()\n<QuerySet [<Reporter: John Smith>]>\n
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Oibríonn comhaireamh sa treo eile i gcomhar le ``difriúil () ``:

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Python console
>>> Reporter.objects.filter(article__headline__startswith="This").count()\n3\n>>> Reporter.objects.filter(article__headline__startswith="This").distinct().count()\n1\n
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Is féidir le ceisteanna dul timpeall i gciorcail:

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Python console
>>> Reporter.objects.filter(article__reporter__first_name__startswith="John")\n<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]>\n>>> Reporter.objects.filter(article__reporter__first_name__startswith="John").distinct()\n<QuerySet [<Reporter: John Smith>]>\n>>> Reporter.objects.filter(article__reporter=r).distinct()\n<QuerySet [<Reporter: John Smith>]>\n
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Má scriosann tú tuairisceoir, scriosfar a n-alt (ag glacadh leis gur sainmhíníodh an ForeignKey le:attr: django.db.models.foreignkey.on_delete socraithe go CASCADE, arb é an réamhshocraithe):

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Python console
>>> Article.objects.all()\n<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>\n>>> Reporter.objects.order_by("first_name")\n<QuerySet [<Reporter: John Smith>, <Reporter: Paul Jones>]>\n>>> r2.delete()\n>>> Article.objects.all()\n<QuerySet [<Article: John's second story>, <Article: This is a test>]>\n>>> Reporter.objects.order_by("first_name")\n<QuerySet [<Reporter: John Smith>]>\n
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Is féidir leat a scriosadh ag baint úsáide as JOIN san fhiosrúchán:

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Python console
>>> Reporter.objects.filter(article__headline__startswith="This").delete()\n>>> Reporter.objects.all()\n<QuerySet []>\n>>> Article.objects.all()\n<QuerySet []>\n
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