Perform OR Condition in Django Queryset

While querying a database using Django's ORM—Object-Relational Mapping—one of the most common requirements would probably be filtering data on more than one condition. By default, Django supports filtering data with AND conditions. However, specific techniques have to be used when you need to filter data with OR conditions. This article is going to walk you through the ways of OR conditions in Django QuerySets with Q objects and how to combine such queries, along with practical examples.

Using Q Objects

These are Django's Q objects, which encapsulate a collection of keyword arguments usable in complex queries. They allow you to perform OR and other complex queries easily.

To use Q objects, you'll need to import them from django.db.models. The Q object allows one to construct complex queries easily by joining several conditions together using the | and & operators. Here is some basic example of using Q objects:

from myapp.models import MyModel
from django.db.models import Q

# Example of an OR condition
queryset = MyModel.objects.filter(Q(field1=value1) | Q(field2=value2))

This example will include all objects in the queryset where field1 equals value1 or field2 equals value2.

Combining Queries

You can sometimes be interested in ORing a bit across multiple queries. This is done by passing querysets to be combined using the | operator. You can do this in the following way:

from myapp.models import MyModel

# First query
queryset1 = MyModel.objects.filter(field1=value1)

# Second query
queryset2 = MyModel.objects.filter(field2=value2)

# Combining queries using OR
combined_queryset = queryset1 | queryset2

The combined_queryset will include all objects from queryset1 and queryset2. This method is useful when you need to perform OR operations across different queries or filters.

Examples to Perform OR Condition in Django Queryset

Example 1: Simple OR Condition

Suppose you have a model Book with the fields title and author. You would want to select all books, either having the title "Django for Beginners" or being authored by "John Doe". You can use the following query:

from myapp.models import Book
from django.db.models import Q

# OR condition using Q objects
books = Book.objects.filter(Q(title="Django for Beginners") | Q(author="John Doe"))

Output:

Example 2: Combining Multiple OR Conditions

Suppose you have a model Product with fields in the category, price, and availability. You would want to return only those products that are either in the "Electronics" category or whose price is less than $100. Here is how:

from myapp.models import Product
from django.db.models import Q

# Combining multiple OR conditions
products = Product.objects.filter(Q(category="Electronics") | Q(price__lt=100))

Output:

Example 3: Combining Queries with OR Condition

If you want to combine results from two different queries, such as getting products in either the "Furniture" category or with availability set to "In Stock", you can do:

from myapp.models import Product

# First query for category
category_query = Product.objects.filter(category="Furniture")

# Second query for availability
availability_query = Product.objects.filter(availability="In Stock")

# Combining the two queries
combined_products = category_query | availability_query

Output:

Conclusion

It is easy to perform OR conditions in Django QuerySets using Q objects or by combining queries. Knowing these techniques will help you derive more flexible and powerful queries within your Django applications. Whether you want to filter data according to multiple conditions or combine results from several queries, these methods will enable you to do things efficiently.