I have two models Article and Blog related using a foreign key. I want to select only blog name while extracting the article.
我有两个模型文章和博客使用一个外键。在提取文章时，我只想选择blog名称。
articles = Articles.objects.all().select_related('blog__name')
The query generated shows that it selected all the fields from the Blog model. I tried using only() and defer() with select_related but both didn't work out.
生成的查询显示它从Blog模型中选择了所有字段。我尝试使用only()和deferred()与select_related结合，但都没有成功。
articles = Articles.objects.all().select_related('blog__name').only('blog__name', 'title', 'create_time')
The above query resulted in error: Invalid field name(s) given in select_related: Choices are: blog
上面的查询导致了错误:select_related: Choices中的字段名无效
How do i generate a query so that only article fields and blog name is selected?
如何生成查询，以便只选择文章字段和博客名称?
2 个解决方案
#1
9
You can use annotate() for this.
您可以为此使用annotate()。
>>> a = Articles.objects.annotate(blog_name=F('blog__name')).first()
>>> a.title
>>> a.blog_name
#2
6
select_related should be use on the whole model, and then you can filter it more. This will work:
select_related应该用于整个模型，然后您可以对它进行更多的过滤。这将工作:
Articles.objects.select_related('blog').only('blog__name', 'title', 'create_time')
#1
9
You can use annotate() for this.
您可以为此使用annotate()。
>>> a = Articles.objects.annotate(blog_name=F('blog__name')).first()
>>> a.title
>>> a.blog_name
#2
6
select_related should be use on the whole model, and then you can filter it more. This will work:
select_related应该用于整个模型，然后您可以对它进行更多的过滤。这将工作:
Articles.objects.select_related('blog').only('blog__name', 'title', 'create_time')