Get count, average, min, max values from model field using Django Aggregate

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

>>> 

To Know more about our Django CRM(Customer Relationship Management) Open Source Package. Check Code

Posted On 25 March 2015 By MicroPyramid


About Micropyramid

Micropyramid is a software development and cloud consulting partner for enterprise businesses across the world. We work on python, Django, Salesforce, Angular, Reactjs, React Native, MySQL, PostgreSQL, Docker, Linux, Ansible, git, amazon web services. We are Amazon and salesforce consulting partner with 5 years of cloud architect experience. We develop e-commerce, retail, banking, machine learning, CMS, CRM web and mobile applications.


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