Django查询多对一关系，如何检索多对一关系的数据

Question

how to retrive data many to one relationship.

class Ads(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    title = models.CharField(max_length=75)

class Aimage(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    ads = models.ForeignKey(Ads, on_delete=models.CASCADE, related_name='ads_image')
    image = models.ImageField(blank=True)

my view:

qs = Ads.objects.all()

template:

{% for o in qs.aimage_set.all %}
{{ o.title }} 
{{ o.image.url }} #does work
{% endfor %}

Answer 1

qs is a set of Ads , so you can not access qs.aimage_set on the queryset but on an Ads model. Furthermore you specified as value for the related_name=… parameter [Django-doc] , related_name='ads_image' , so this it the name of the manager to access the objects in reverse:

{% for ad in qs %}
    <b>{{ o.title }}</b>
    {% for o in .all %}
        {{ o.image.url }}
    {% endfor %}
{% endfor %}

This will result in an N+1 problem. You can use .prefetch_related(…) [Django-doc] to fetch the related Aimage objects in bulk :

qs = Ads.objects