Question

示例代码

class Person(models.Model):
    name = models.CharField(max_length=100)

class Post(models.Model):
    author = models.ForeignKey(Person)
    content = models.TextField()

class Comment(models.Model):
    post = models.ForeignKey(Post)
    author = models.ForeignKey(Person)
    content = models.TextField()


foo = Person.objects.create(name='foo')
bar = Person.objects.create(name='bar')

blog = Post.objects.create(author=foo,content='Random Blog 1')
blog2 = Post.objects.create(author=foo, content='Radom Blog 2')

c1 = Comment.objects.create(post=blog, author=foo, content='Comment on blog1')
c2 = Comment.objects.create(post=blog, author=bar, content='Bar comment on blog1')
c3 = Comment.objects.create(post=blog2, author=foo, content='Comment on blog2')
c4 = Comment.objects.create(post=blog2, author=bar, content='Bar comment on blog2')

如何创建一个返回所有Post的作者foo的查询，并且每个Post的comment_set中的Comment仅由foo创建。

Answer 1

我可能会这样做：

    from django.db.models import Count, F

    Post.objects.filter(author=foo
        ).annotate(comment_count=Count('comment_set')
        ).filter(comment_set__author=foo #
        ).annotate(foo_comment_count=Count('comment_set')
        ).filter(foo_comment_count=F('comment_count')))

另一种方法是子查询，选择由其他人评论的帖子然后foo，然后选择所有不在该组中的PK。

使用Django的ORM编写查询与编写SQL查询没有太大区别。作为最后的手段，您总是可以写一个raw query。

Django：对相关模型进行限制查询

1 个答案: