Django Query with Q objects

runQquery.py

from django.db.models.query import Q
from django.db import models


# to query a database table, you can use the Django ORM.
# assuming you have a table called "users" with the following fields:
class User(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    email = models.EmailField(max_length=254)
    password = models.CharField(max_length=50)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.first_name
    

class Profile(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    bio = models.TextField(max_length=500, blank=True)
    
    
# to query a database table, you can use the Django ORM.
# query for email that starts with "a" and last name that starts with "b"
user = User.objects.filter(email__istartswith='a', last_name__istartswith='b')

# query for email that starts with "a" or last name that starts with "b"
user = User.objects.filter(Q(email__istartswith='a') | Q(last_name__istartswith='b'))
# in the above example, the query is equivalent to:
user = User.objects.filter(email__istartswith='a') | User.objects.filter(last_name__istartswith='b')
# but the above query is more efficient than the following:
user = User.objects.filter(Q(email__istartswith='a') & Q(last_name__istartswith='b'))

# using select_related() get the related object
user = User.objects.select_related('profile').filter(email__istartswith='a')
# or
user = User.objects.filter(email__istartswith='a').select_related('profile')

# using prefetch_related() get the related object
user = User.objects.prefetch_related('profile').filter(email__istartswith='a')
# or
user = User.objects.filter(email__istartswith='a').prefetch_related('profile')