QuerySet

 models.py

from django.db import models

from django.contrib.auth.models import User

from django.core.validators import MinValueValidator, MaxValueValidator

from django.core.exceptions import ValidationError

def validate_restaurant_name_begins_with_a(value):

    if not value.startswith('a'):

        raise ValidationError('Restaurant name must begin with "a"')

class Restaurant(models.Model):

    class TypeChoices(models.TextChoices):

        INDIAN = 'IN', 'Indian'

        CHINESE = 'CH', 'Chinese'

        ITALIAN = 'IT', 'Italian'

        GREEK = 'GR', 'Greek'

        MEXICAN = 'MX', 'Mexican'

        FASTFOOD = 'FF', 'Fast Food'

        OTHER = 'OT', 'Other'

    name = models.CharField(max_length=100, validators=[validate_restaurant_name_begins_with_a])

    website = models.URLField(default='')

    date_opened = models.DateField()

    latitude = models.FloatField(validators=[MinValueValidator(-90), MaxValueValidator(90)])

    longitude = models.FloatField(validators=[MinValueValidator(-180), MaxValueValidator(180)])

    restaurant_type = models.CharField(max_length=2, choices=TypeChoices.choices)

    def __str__(self):

        return self.name

class Rating(models.Model):

    user = models.ForeignKey(User, on_delete=models.CASCADE)

    restaurant = models.ForeignKey(Restaurant, on_delete=models.CASCADE, related_name='ratings')

    rating = models.PositiveSmallIntegerField(

        validators=[MinValueValidator(1), MaxValueValidator(5)]

    )

    def __str__(self):

        return f"Rating: {self.rating}"

   

class Sale(models.Model):

    restaurant = models.ForeignKey(

        Restaurant, on_delete=models.SET_NULL, null=True, related_name='sales')

    income = models.DecimalField(max_digits=8, decimal_places=2)

    datetime = models.DateTimeField()

views.py

How to access parent model to child model using for loop .py file

Here "ratings" related_name

    restaurants = Restaurant.objects.all()# filter(name__istartswith='a')

    for i in restaurants:

        for j in i.ratings.all():

            print(j.rating)

How to access parent model to child model using for loop .html file

        {% for res in restaurants %}

            <p>{{res.name}}</p>

             <ul>

                {% for rat in res.ratings.all %}

                    <li>{{rat.rating}}</li>

                {% endfor %}

            </ul>

         {% endfor %}

How to access parent and child togather like object in .py file