DjangoにおけるデータベースのSELECT, INSERT, UPDATE, DELETE

from django.db import models
from datetime import datetime

class User(models.Model):

    user_name = models.CharField(primary_key=True, max_length=100)

    password = models.CharField(max_length=100)

    created_at = models.DateTimeField(default=datetime.now)

    class Meta:
        
        db_table = 'User'

from django.views.generic import TemplateView
from test_app.models.user import User

class RegistView(TemplateView):

    def post(self, request, *args, **kwargs):

        users = User.objects.all().filter(user_name='aaa').order_by('created_at')

        context = {
            'users': users,
        }

        template_name = 'test_app/index.html'

        return render(request, template_name, context)

from django.views.generic import TemplateView
from test_app.models.user import User

class RegistView(TemplateView):

    def post(self, request, *args, **kwargs):

        user_name = request.POST['user_name']
        password = request.POST['password']

        user = User(user_name=user_name, password=password)
        user.save()

        ...

from django.views.generic import TemplateView
from test_app.models.user import User

class RegistView(TemplateView):

    def post(self, request, *args, **kwargs):

        users = User.objects.all().filter(user_name='aaa').update(user_name='iii')

        ...

from django.views.generic import TemplateView
from test_app.models.user import User

class RegistView(TemplateView):

    def post(self, request, *args, **kwargs):

        users = User.objects.update_or_create(
                first_name='Tarou2', last_name='Tanaka'2,
                defaults={'first_name': 'Tarou1'},
            )

        ...