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Diffstat (limited to 'docs/ref')
| -rw-r--r-- | docs/ref/contrib/postgres/aggregates.txt | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/docs/ref/contrib/postgres/aggregates.txt b/docs/ref/contrib/postgres/aggregates.txt index d8964115e0..55ec952fa2 100644 --- a/docs/ref/contrib/postgres/aggregates.txt +++ b/docs/ref/contrib/postgres/aggregates.txt @@ -208,6 +208,32 @@ General-purpose aggregation functions Examples are the same as for :attr:`ArrayAgg.ordering`. + Usage example:: + + class Publication(models.Model): + title = models.CharField(max_length=30) + + class Article(models.Model): + headline = models.CharField(max_length=100) + publications = models.ManyToManyField(Publication) + + >>> article = Article.objects.create(headline="NASA uses Python") + >>> article.publications.create(title="The Python Journal") + <Publication: Publication object (1)> + >>> article.publications.create(title="Science News") + <Publication: Publication object (2)> + >>> from django.contrib.postgres.aggregates import StringAgg + >>> Article.objects.annotate( + ... publication_names=StringAgg( + ... "publications__title", + ... delimiter=", ", + ... ordering="publications__title", + ... ) + ... ).values("headline", "publication_names") + <QuerySet [{ + 'headline': 'NASA uses Python', 'publication_names': 'Science News, The Python Journal' + }]> + .. deprecated:: 4.0 If there are no rows and ``default`` is not provided, ``StringAgg`` |