? QuerySet Filtering in Django

? Quick Overview

Django QuerySets allow you to retrieve and manipulate database records efficiently. Common filtering methods like filter(), get(), and exclude() help narrow down results based on conditions.

? Key Concepts

• QuerySets are lazy and chainable
• Filtering does not hit the database immediately
• Each method returns a new QuerySet

? Syntax / Theory

QuerySet methods apply SQL-like conditions using Pythonic syntax with field lookups.

? filter() Method

# Filter products using conditions
from .models import Product
products = Product.objects.filter(price__gt=100)
products_in_category = Product.objects.filter(category='Electronics')

? get() Method

# Retrieve a single unique object
from .models import Product
product = Product.objects.get(id=1)
product_by_name = Product.objects.get(name='Laptop')

? exclude() Method

# Exclude matching records
from .models import Product
products_not_in_category = Product.objects.exclude(category='Electronics')
products_above_50 = Product.objects.exclude(price__lt=50)

? Combining QuerySet Methods

# Chain multiple QuerySet methods
from .models import Product
products = Product.objects.filter(category='Electronics', price__gt=100)\
.exclude(stock=0)\
.order_by('price')

? Live Output / Explanation

Each chained method refines the query. Django executes the final SQL query only when data is accessed.

?️ Interactive Simulator

? Use Cases

• Filtering products by price or category
• Fetching a single record safely
• Excluding invalid or inactive records