Re: Perform a join in 5 tables or more than that USIN ORM

from django.db import models
from django.conf import settings
from django.db.models.signals import pre_save
from django.utils.text import slugify
from django.dispatch import receiver
# Create your models here.

class course_categories(models.Model):
deleted_flag = [('y', 'yes'), ('n', 'no')]
category_name = models.CharField(max_length=50, unique=True)
category_slug = models.SlugField(max_length=100, unique=True)
course_categories_code = models.CharField(max_length=7, unique=True)
created_by = models.CharField(max_length=50, null=True, blank=True)
created_date = models.DateTimeField(auto_now_add=True)
modified_by = models.CharField(max_length=50, blank=True, null=True)
modified_date = models.DateTimeField(
auto_now_add=False, blank=True, null=True)
is_deleted_flag = models.CharField(
max_length=1, choices=deleted_flag, default='n')

def __str__(self):
return self.category_name

def create_course_category_slug(instance, new_slug=None):

slug = slugify(instance.category_name)
if new_slug is not None:
slug = new_slug
slug = "%s-%s" % (slug, instance.course_categories_code)
qs = course_categories.objects.filter(category_slug=slug).order_by("-id")
exists = qs.exists()
if exists:
new_slug = "%s-%s" % (slug, qs.first().id)
return create_course_category_slug(instance, new_slug=new_slug)
print("slug", slug)
return slug

@receiver(pre_save, sender=course_categories)
def pre_save_course_categories_receiver(sender, instance, *args, **kwargs):
# if not instance.category_slug:
instance.category_slug = create_course_category_slug(instance)

class courses(models.Model):
deleted_flag = [('y', 'yes'), ('n', 'no')]
course_name = models.CharField(max_length=70)
course_categories = models.ForeignKey(
'course_categories', related_name='courses', on_delete=models.CASCADE)
course_slug = models.SlugField(unique=True)
course_code = models.CharField(max_length=7, unique=True)
created_by = models.CharField(max_length=50, null=True, blank=True)
created_date = models.DateTimeField(auto_now_add=True)
modified_by = models.CharField(max_length=50, blank=True, null=True)
modified_date = models.DateTimeField(
auto_now_add=False, blank=True, null=True)
is_deleted_flag = models.CharField(
max_length=1, choices=deleted_flag, default='n')

def __str__(self):
return self.course_name

def create_course_slug(instance, new_slug=None):

slug = slugify(instance.course_name)
if new_slug is not None:
slug = new_slug
slug = "%s-%s" % (slug, instance.course_code)
qs = courses.objects.filter(course_slug=slug).order_by("-id")
exists = qs.exists()
if exists:
new_slug = "%s-%s" % (slug, qs.first().id)
return create_course_slug(instance, new_slug=new_slug)
print("slug", slug)
return slug

@receiver(pre_save, sender=courses)
def pre_save_course_receiver(sender, instance, *args, **kwargs):
# if not instance.category_slug:
print("course")
instance.course_slug = create_course_slug(instance)

class subcourse(models.Model):
deleted_flag = [('y', 'yes'), ('n', 'no')]
subcourse_name = models.CharField(max_length=50, unique=True)
courses = models.ForeignKey(
'courses', related_name="subcourse", on_delete=models.CASCADE)
subcourse_slug = models.SlugField(unique=True)
subcourse_code = models.CharField(max_length=7, unique=True)
subcourse_short_description = models.CharField(max_length=150, blank=True)
created_by = models.CharField(max_length=50)
created_date = models.DateTimeField(auto_now_add=True)
modified_by = models.CharField(max_length=50, blank=True, null=True)
modified_date = models.DateTimeField(
auto_now_add=False, blank=True, null=True)
is_deleted_flag = models.CharField(
max_length=1, choices=deleted_flag, default='n')

def __str__(self):
return self.subcourse_name

def create_subcourse_slug(instance, new_slug=None):

slug = slugify(instance.subcourse_name)
if new_slug is not None:
slug = new_slug
slug = "%s-%s" % (slug, instance.subcourse_code)
qs = subcourse.objects.filter(subcourse_slug=slug).order_by("-id")
exists = qs.exists()
if exists:
new_slug = "%s-%s" % (slug, qs.first().id)
return create_subcourse_slug(instance, new_slug=new_slug)
print("slug", slug)
return slug

@receiver(pre_save, sender=subcourse)
def pre_save_subcourse_receiver(sender, instance, *args, **kwargs):
# if not instance.category_slug:
print("course")
instance.subcourse_slug = create_subcourse_slug(instance)

class course_description(models.Model):
pass
from rest_framework import serializers
from .models import course_categories, courses, subcourse
from course_setup.serializers import MainTopicSerializer

class CourseCategorySerializerRedesign(serializers.ModelSerializer):
value = serializers.IntegerField(source="id")
label = serializers.CharField(source="category_name")

class Meta:
model = course_categories
fields = ('value', 'label')

class SubCourseSerializers(serializers.ModelSerializer):
course_name = serializers.SerializerMethodField(read_only=True)
subcourse_main_topic = MainTopicSerializer(many=True)
class Meta:
model = subcourse
fields = ('id', 'subcourse_name', 'courses', 'subcourse_slug', 'subcourse_code',
'subcourse_short_description', 'courses', 'course_name','subcourse_main_topic')

def get_course_name(self, instance):
return instance.courses.course_name

class CourseSerializerView(serializers.ModelSerializer):
# subcourse = SubcourseSerializerView()

class Meta:
model = courses
fields = ('id', 'course_name', 'course_code', 'course_categories')

class SubcourseSerializerView(serializers.ModelSerializer):
# courses = CourseSerializerView()

class Meta:
model = subcourse
fields = ('id', 'subcourse_name',
'subcourse_code', 'courses')
# depth = 2

class CourseSerializers(serializers.ModelSerializer):
subcourse = SubCourseSerializers(many=True, read_only=True)

class Meta:
model = courses
fields = ('__all__')

class CourseCategorySerializers(serializers.ModelSerializer):
# courses = CourseSerializers(many=True)

class Meta:
model = course_categories
fields = ('id', 'category_name', 'course_categories_code')

class GetCourseCategorySerializer(serializers.ModelSerializer):

class Meta:
model = course_categories
fields = ('id', 'category_name', 'course_categories_code',
'category_slug')

class CourseCategoryTreeSerializer(serializers.ModelSerializer):
courses = serializers.SerializerMethodField('get_children')

def get_children(self, course_categories):
serialized_data = CourseSerializers(course_categories.courses.all(
), many=True, read_only=True, context=self.context)
return serialized_data.data

class Meta:
model = course_categories
fields = ('id', 'category_name', 'course_categories_code',
'category_slug', 'courses')
from dataclasses import fields
from pyexpat import model
from rest_framework import serializers
from .models import subcourse_main_topic,sub_topic,subcourse


class MainTopicSerializer(serializers.ModelSerializer):
class Meta:
model = subcourse_main_topic
fields='_all_'

class SubTopicSerializer(serializers.ModelSerializer):
class Meta:
model = sub_topic
fields='_all_'from django.db import models
from course_category.models import subcourse
from instructors.models import instructor
# Create your models here.
deleted_flag = [('y', 'yes'), ('n', 'no')]
class subcourse_main_topic(models.Model):
subcourse = models.ForeignKey('course_category.subcourse',related_name="subcourse",on_delete=models.CASCADE)
topic_title = models.CharField(max_length=255)
created_by = models.CharField(max_length=100)
created_date = models.DateTimeField(auto_now_add=True)
modified_by = models.CharField(max_length=100)
modified_date = models.DateTimeField(auto_now_add=True)
modified_remarks = models.CharField(max_length=255,blank=True,null=True)
is_deleted_flag = models.CharField(
max_length=1, choices=deleted_flag, default='n')

class sub_topic(models.Model):
subcourse_main_topic_id = models.ForeignKey('subcourse_main_topic',related_name="subtopic",on_delete=models.CASCADE)
topic_title = models.CharField(max_length=255)
video_url = models.URLField()
preview_status = models.BooleanField(default=False)
resource_url = models.URLField(null=True,blank=True)
instructors = models.ForeignKey('instructors.instructor',related_name="instructors",on_delete=models.CASCADE)
created_by=models.CharField(max_length=70)
created_date = models.DateTimeField(auto_now_add=True)
modified_by = models.CharField(max_length=70,null=True,blank=True)
modified_date = models.DateTimeField(null=True,blank=True)
modified_remarks = models.CharField(max_length=150,null=True,blank=True)
is_deleted_flag = models.CharField(
max_length=1, choices=deleted_flag, default='n')from django.shortcuts import render
import base64
from .serializers import (
CourseCategorySerializers,
GetCourseCategorySerializer,
CourseSerializers,
CourseCategorySerializerRedesign,
CourseCategoryTreeSerializer,
SubCourseSerializers,
CourseSerializerView,
SubcourseSerializerView
)
from rest_framework.response import Response
from rest_framework.decorators import api_view
from rest_framework import status
from rest_framework.parsers import JSONParser
from .models import course_categories, courses, subcourse
from rest_framework.generics import ListAPIView
from django.db.models import Prefetch
# Create your views here.

@api_view(['GET'],)
def get_all_course_category(request):
result = {
'data': '',
'response': False,
'msg': 'Operation Failed !!'
}
queryset = course_categories.objects.all()
serializer = GetCourseCategorySerializer(queryset, many=True)
print(serializer.data)
# serializer.data['enc_id'] = base64.standard_b64encode(serializer.data.id)
result = {
'data': serializer.data,
'response': True,
'msg': ''
}
# return Response({'course_category': serializer.data})
return Response(result)

@api_view(['POST'])
def create_course_category_serializer(request):
result = {
'data': '',
'response': False,
'msg': 'Opertaion Failed !!'
}
if request.method == 'POST':
serializer = CourseCategorySerializers(
data=request.data)
if serializer.is_valid():
serializer.save()
result = {
'data': serializer.data,
'response': True,
'msg': 'Course category added successfully !!'
}
return Response(result, status=status.HTTP_200_OK)
result = {
'data': serializer.errors,
'response': False,
'msg': 'Operation Failed !!',
'type': 'form-error'
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)

@api_view(['GET'],)
def get_course_category_by_id(request, slug):
# print("slug", slug)
result = {
'data': '',
'response': False,
'msg': 'Operation Failed !!'
}
try:
queryset = course_categories.objects.get(category_slug=slug)
# print("queryset", queryset)
serializer = GetCourseCategorySerializer(queryset, many=False)
result = {
'data': serializer.data,
'response': True,
'msg': ''
}
return Response(result)
except course_categories.DoesNotExist:
result = {
'data': serializer.errors,
'response': False,
'msg': 'Data Doesnot exist !!'
}
return Response(result)

@api_view(['PATCH'])
def update_course_category_serializer(request):
if request.method == "PATCH":
result = {
'data': '',
'response': False,
'msg': 'Operation Failed !!'
}
category_id = request.data['category_id']
try:
category_data = course_categories.objects.get(pk=category_id)
serializer = CourseCategorySerializers(category_data, request.data)
if(serializer.is_valid()):
serializer.save()
result = {
'data': serializer.data,
'response': True,
'msg': 'Updated Successfully !!'
}
return Response(result, status=status.HTTP_200_OK)
result = {
'data': serializer.errors,
'response': False,
'msg': 'Operation Failed !!',
'type': 'form-error'
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)
except course_categories.DoesNotExist:
result = {
'data': request.data,
'response': False,
'msg': 'Data Doesnot exist !!'
}
return Response(result)

@api_view(['GET', ])
def get_course_category_select(request):
queryset = course_categories.objects.all()
serializer = CourseCategorySerializerRedesign(queryset, many=True)
return Response({'course_category': serializer.data})

@api_view(['GET', ])
def get_all_course(request):
result = {
'data': '',
'response': False,
'msg': 'Opertaion Failed !!'
}
queryset = courses.objects.all()
serializer = CourseSerializers(queryset, many=True)
result = {
'data': serializer.data,
'response': True,
'msg': ''
}
return Response(result)

@api_view(['POST', ])
def create_course(request):
result = {
'data': '',
'response': False,
'msg': 'Opertaion Failed !!'
}
if request.method == "POST":
serializer = CourseSerializerView(data=request.data)
if (serializer.is_valid()):
serializer.save()
result = {
'data': serializer.data,
'response': True,
'msg': 'Course Added Successfully !!'
}
return Response(result, status=status.HTTP_200_OK)
result = {
'data': serializer.errors,
'response': False,
'msg': ''
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)

@api_view(['GET', ])
def get_course_by_id(request, slug):
if request.method == 'GET':
result = {
'data': '',
'response': False,
'msg': 'Opertaion Failed !!'
}
try:
print("slug", slug)
getData = courses.objects.get(course_slug=slug)
serializer = CourseSerializers(getData, many=False)

result = {
'data': serializer.data,
'response': True,
'msg': ''
}
return Response(result, status=status.HTTP_200_OK)
except courses.DoesNotExist:
result = {
'data': '',
'response': False,
'msg': 'Data Doesnot exist'
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)

@api_view(['PATCH', ])
def edit_course(request):
if request.method == "PATCH":
result = {
'data': '',
'response': False,
'msg': 'Opertaion Failed !!'
}
try:
course_id = request.data['course_id']
checkData = courses.objects.get(pk=course_id)
serializer = CourseSerializerView(checkData, request.data)
data = {}
if serializer.is_valid():
serializer.save()
result = {
'data': serializer.data,
'response': True,
'msg': 'updated successfully !!'
}
return Response(result, status=status.HTTP_200_OK)
result = {
'data': serializer.errors,
'response': False,
'msg': ''
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)
except courses.DoesNotExist:
result = {
'data': '',
'response': False,
'msg': 'Data doesnot exist'
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)

@api_view(['GET', ])
def get_all_sub_course(request):
result = {
'data': '',
'response': False,
'msg': 'Opertaion Failed !!'
}
queryset = subcourse.objects.select_related(
'courses')
serializers = SubCourseSerializers(queryset, many=True)
result = {
'data': serializers.data,
'response': True,
'msg': ''
}
return Response(result, status=status.HTTP_200_OK)

@api_view(['POST', ])
def create_sub_course(request):
result = {
'data': '',
'response': False,
'msg': 'Operation Failed'
}
if request.method == "POST":
serializer = SubcourseSerializerView(data=request.data)
if serializer.is_valid():
serializer.save()
result = {
'data': serializer.data,
'response': True,
'msg': 'Subcourse created successfully !!'
}
return Response(result, status=status.HTTP_200_OK)
result = {
'data': serializer.errors,
'response': False,
'msg': ''
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)

@api_view(['GET', ])
def get_sub_course_by_slug(request, slug):
result = {
'data': '',
'response': False,
'msg': 'Operation Failed!!'
}
if request.method == "GET":
try:
data = subcourse.objects.get(subcourse_slug=slug)
serializer = SubCourseSerializers(data, many=False)
result = {
'data': serializer.data,
'response': True,
'msg': ''
}
return Response(result, status=status.HTTP_200_OK)
except subcourse.DoesNotExist:
result = {
'data': '',
'response': False,
'msg': 'Data Doesnot Exist '
}
return Response(result)

@api_view(['PATCH', ])
def edit_subcourse(request):
result = {
'data': '',
'response': False,
'msg': 'Operation Failed !!'
}
if request.method == "PATCH":
try:
subcourse_id = request.data['subcourse_id']
checkData = subcourse.objects.get(pk=subcourse_id)
serializer = SubcourseSerializerView(checkData, data=request.data)
if serializer.is_valid():
serializer.save()
result = {
'data': serializer.data,
'response': True,
'msg': 'Updated Successfully !!'
}
return Response(result, status=status.HTTP_200_OK)
result = {
'data': serializer.errors,
'response': False,
'msg': ''
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)
except subcourse.DoesNotExist:
result = {
'data': request.data,
'response': False,
'msg': 'Data Doesnot exist !!'
}
return Response(result, status=status.HTTP_400_BAD_REQUEST)

@api_view(['GET', ])
def get_course_tree_view(request):
# queryset = course_categories.objects.prefetch_related('courses')

children = Prefetch(
'courses__subcourse', queryset=subcourse.objects.select_related('courses'))
queryset = course_categories.objects.prefetch_related(children)
serializer = CourseCategoryTreeSerializer(queryset, many=True)

return Response(serializer.data)

here are my models serializers and views and i need a data in tree structure. the function in view file is get_course_tree_view

and rest are the models and serializers I need to join all these tables together to fetch data i was able to do only three joins

On Sun, Jan 30, 2022 at 8:37 PM Sam Chaffy <joezeppe.code@gmail.com> wrote:

Yes you can 

What's your model look like ?

On Sun, Jan 30, 2022 at 7:26 AM narendra...@gmail.com <narendrathapa222@gmail.com> wrote:

hello folks,

 any django ex[ert here, I want to know if anybody can do multiple join more than 5 tables at once using ORM Prefetch,prefetch_related,select_related using any of these or in a different way please ping, or just write over here how can we solve that. i didn't get any clue

help will be appreciated

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Oussama Chafiqui

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