To define a many-to-one relationship, use ForeignKey:
If a model has a ForeignKey, instances of that model will have access to the related (foreign) object via an attribute of the model.
from django.db import models
class Skill(models.Model):
name = models.CharField(max_length=256)
def __str__(self):
return self.name
class Subskill(models.Model):
skill = models.ForeignKey(Skill, on_delete=models.CASCADE)
name = models.CharField(max_length=256)
def __str__(self):
return self.name
View
def home(request):
skills = Skill.objects.all().prefetch_related('subskill_set') # optimizing
context = {'skills':skills}
return render(request, 'skill.html', context)
In template
{% for skill in skills %}
{{skill.name}}
{% for subskill in skill.subskill_set.all %}
{{subskill.name}}
{% endfor %}
{% endfor %}
Get by order
sample_object.users_set.all()[0]
# in template
{{ sample_object.users_set.all.0 }}
# another example in template
# TranstorPrice has Translator fk
{% for price in translator.translatorprice_set.all %}
{{price}}
{% endfor %}
Following relationships “backward”
b = Blog.objects.get(id=1)
b.entry_set.all() # Returns all Entry objects related to Blog.
Filter
class Car(models.Model):
name = models.CharField(max_length=255)
class CarModel(models.Model):
name = models.CharField(max_length=255)
car = models.ForeignKey(Car, on_delete=models.SET_NULL, blank=True, null=True)
mercedes.carmodel_set.all()
mercedes.carmodel_set.first()
mercedes.carmodel_set.first().name
Filter car_models by car:
CarModel.objects.filter(car__name="Mercedes")
Filter cars by car_models:
Car.objects.filter(carmodel__name="C180")
Translator has many prices
filtered_prices_by_source = TranslatorPrice.objects.filter(source_language= source_language)
filtered_translators = filtered_translators.filter(translatorprice__in=filtered_prices_by_source).distinct()
