How to Perform GROUP BY Queries in Django?

How to Achieve Group By Query in Django?

In Django, to perform a group by query on a model, one can employ the aggregation features of the ORM. This is achieved by utilizing the values() and annotate() methods.

Consider the following example:

from django.db.models import Count
result = (Members.objects
    .values('designation')
    .annotate(dcount=Count('designation'))
    .order_by()
)

This code translates to a SQL query similar to:

SELECT designation, COUNT(designation) AS dcount
FROM members GROUP BY designation

The result of the query will be a list of dictionary objects, each representing a group. For instance:

[{'designation': 'Salesman', 'dcount': 2}, 
 {'designation': 'Manager', 'dcount': 2}]

To include multiple fields in the results, simply add them as arguments to values():

    .values('designation', 'first_name', 'last_name')

References:

• Django documentation: values(), annotate(), and Count
• Django documentation: Aggregation, especially the section on Interaction with default ordering or order_by()

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