How Can I Combine Two or More QuerySets in a Django View?

James W.

The Problem

You know that Django allows for the creation of QuerySets from the database by making use of methods like filter() or exclude().

But can we create a QuerySet out of a combination of other QuerySets?

Say we wanted to create a QuerySet from data collected from two different models. The use of the filter() and exclude() methods would not help here.

Or we might be creating a QuerySet with complex inclusions and exclusions using the filter() and exclude() methods, and it would be simpler to create multiple QuerySets and then combine them into a single set.

The Solution

It is possible to combine QuerySets into another QuerySet, and they do not have to be from the same model.

The Python union operator can be used to combine QuerySets that belong to the same model.

Two or more QuerySets can be combined using the union operator with the following syntax:

model_combination = model_set1 | model_set2 | model_set3

You can also use the chain() method from the Itertools module, which allows you to combine two or more QuerySets from different models through concatenation.

from itertools import chain

model_combination = list(chain(model_set1, model_set2))

Alternatively, you can use union() to combine two or more QuerySets from different models, passing all=TRUE if you want to allow duplicates.

model_combination = model_set1.union(model_set2, all=TRUE)

Further Reading

For some tips on working with Django on Sentry, have a look at these articles:

• Monitoring Performance and Errors in a Django Application with Sentry
• Finding and Fixing Django N+1 Problems
• Debug Issues Faster with Breadcrumbs