如何在多对多字段中查询具有所有给定对象的对象？

Question

I was trying to find out one way where I can query all the objects of one table which are having the given objects as ManyToMany Field.

Please take below example:

class Post(models.Model):
    title = models.CharField(max_length=50)
    text = models.CharField(max_length=1000)
    pub_date = models.DateTimeField('date published')
    author = models.CharField(max_length=30)
    mail = models.EmailField()

class Tag(models.Model):
    name = models.CharField(max_length=15)
    posts = models.ManyToManyField(Post, related_name="tags")

Here I want to fetch all the posts having both "python" and "django" in the tag list. I can do that at the python level by fetching all the Posts and then checking their tags.

is there any way we can directly fetch it from the DB? Using the DJango QuerySet.

Any help would be appreciated!!

Thanks in Advance!!

Answer 1

Yes, you can try the following -

from django.db.models import Q

filteredPosts = Post.objects.filter(Q(tags__name='python')|Q(tags__name='django'))

Hope it helps

Answer 2

Try this:

Post.objects.filter(id__in=list(Tag.objects.filter(name__in=['Python', 'Django']).values_list('posts', flat=True)))

UPDATE:

Q1 = Tag.objects.filter(name__exact='Django').values_list('posts', flat=True)
Q2 = Tag.objects.filter(name__exact='Python').values_list('posts', flat=True)
Post.objects.filter(id__in=list(set(Q2) & set(Q1)))

Answer 3

Using a Q object you can query for Post objects which both have "python" AND "django" like this:

from django.db.models import Q

qs = Post.objects.filter(Q(tags__name='python') & Q(tags__name='django'))

More information about how to make complex queries using the Q object in the docs