Get data from two tables using foreign key in Django - django-models

Question

I have a vendor table it has following structure:
id vendor_name
I have another table named purchases that have the following structure:
id product_id us er_id vendor_id
Then, there is auth_user table by default that has users email address, first_name, last_name etc.
I need to create an API in django class based so that I can get users email address, first_name, last_name etc. based on vendor_id column that is in purchase table when I use GET /vendor/{vendor_id}
Note: I need this API to be created in class based model and views:
My code:
model.py
class Vendor(models.Models):
vendor_name = models.CharField(max_length=25)
class Meta:
ordering = ('vendor_name',)
def __str__(self):
return self.vendor_name
class Purchases(models.Models):
user = models.OneToOneFiled(User, on_delete=models.CASECADE)
product_id = models.ForeignKey('Product', on_delete=models.SET_NULL, null=True, blank=True)
vendor_id = models.ForeignKey('Vendor', on_delete=models.SET_NULL, null=True, blank=True)
def __str__(self):
return self.vendor_id
views.py
class VendorDetail(generics.RetrieveUpdateDestoryAPIView):
queryset= Vendor.objects.all()
serializer_class = VendorSerializer
name = 'vendor-details'
I want JSON response as below. Also, I want the fields to be in same order as below:
{
"id": 1,
"name": "group-1"
"users": [
{
"id": 1,
"email": "abc#gmail",
"first_name": "myfirstname1",
"last_name": "mylastname1" },
{
"id": 2,
"email": "xyz#gmail",
"first_name": "myfirstname2",
"last_name": "mylastname2"
}
],
}

Answer 1

you can get all data by using values
In your Purchases model change vendor_id line like this;
vendor_id = models.ForeignKey('Vendor', on_delete=models.SET_NULL, null=True, blank=True, related_name='vendor_purchases')
And then you can get all data like this; NOTE if you do not use prefetch_related in for loop it access database for each user but now for all data it access database only 3 times
vendor = Vendor.objects.get(pk=vendor_id).prefetch_related(vendor_purchases).prefetch_related(vendor_purchases__user)
user_list = []
for purchase in vendor.vendor_purchases.all():
purchase_user = {}
purchase_user["id"] = purchase.user.pk
purchase_user["email"] = purchase.user.email
purchase_user["first_name"] = purchase.user.first_name
purchase_user["last_name"] = purchase.user.last_name
user_list.append(purchase_user)
result={}
result["id"] = vendor.pk
result["name"] = vendor.name
result["users"] = user_list