Retrieve average, minimum, maximum values from model field using Django Aggregation

Reading Time : ~ .

Django queries help to create, retrieve, update and delete objects. But sometimes we need to get summered values from the objects. Then a Simple solution is to use Django aggregate feature Here are simple examples of how to use aggregation.

app/models.py

class company(models.Model):

    name=models.CharField(max_length=20)

    est=models.IntegerField(max_length=4)

class feature(models.Model):

    name=models.CharField(max_length=20)

class device(models.Model):

    name=models.CharField(max_length=20)

    Code=models.IntegerField()

    Company=models.ForeignKey(company)

    features=models.ManyToManyField(feature)

To perform Min Max and Avg on specific column

 

>>> from django.db.models import Avg, Max, Min, Sum
>>> device.objects.all().aggregate(Avg('price'))
    {'price__avg': 12234.0}
>>> device.objects.all().aggregate(Max('price'))
    {'price__max':587961 }
>>> device.objects.all().aggregate(Min('price'))
{'price__min': 01245}

To know the children count of a foreign key field. 

>>> Comp_Devices=company.objects.annotate(no_of_devices=Count('device'))
>>> Comp_Devices[0].no_of_devices
36
>>> Comp_Devices[0].name
u'Micro'
>>> Comp_Devices[1].no_of_devices
1

the same procedure can be followed for ManyToMany field Columns

>>> Dev_features_count = device.objects.annotate(num=Count('features'))

>>> Dev_features_count[0].num

3

>>> Dev_features_count[1].num

2

>>> 

 

You can perform some complex queries like

To know the devices which have more than two features

>>> Dev_features= device.objects.annotate(num=Count('features')).filter(num__gt=2)

>>> Dev_features[0].num

3

>>> 
    By Posted On
SENIOR DEVELOPER at MICROPYRAMID

Need any Help in your Project?Let's Talk

Latest Comments
Related Articles
Custom Password Less Authentication in Django Nikhila Mergu

Authentication backends allow the ability to change what method checks your users credentials.

For web services, ie Facebook authentication, you don't have access to user ...

Continue Reading...
How to Document API Requests using Django Rest Swagger Swetha Naretla

Django Rest Swagger is used to Document your API for eg., Listing all Your project Rest API's in the browser with brief description about the ...

Continue Reading...
Introduction to API development with Django REST framework Anjaneyulu Batta

Introduction to API development with Django REST framework. You can build the API for any Django application. Pre-requisites are Django and OOPS(object oriented programming concepts) ...

Continue Reading...

Subscribe To our news letter

Subscribe to our news letter to receive latest blog posts into your inbox. Please fill your email address in the below form.
*We don't provide your email contact details to any third parties