Query-related tools in django
In Django, the
QuerySet the object represents a collection of objects from your database. You can use various methods and functions provided by Django to manipulate and retrieve data from these
QuerySets. Some common methods and functions for working with
filter(): Returns a new
QuerySetcontaining object that matches the given criteria.
exclude(): Returns new
QuerySetcontaining objects that do not match given criteria.
order_by(): Returns a new
QuerySetcontaining object ordered according to a given field.
reverse(): Returns a new
QuerySetcontaining object in reverse order.
count(): Returns the number of objects in the
first(): Returns the first object in the
last(): Returns the last object in the
none(): Returns an empty
You can chain these methods together to create more complex queries. For example:
# Get all the articles written by a particular author and order them by the date they were published articles = Article.objects.filter(author='John Smith').order_by('published_date') # Get the number of articles written by a particular author num_articles = Article.objects.filter(author='John Smith').count()
You can also use the
Q objects provided by Django to create more complex queries. For example:
from django.db.models import Q # Get all the articles written by either John Smith or Jane Smith articles = Article.objects.filter(Q(author='John Smith') | Q(author='Jane Smith')) # Get all the articles with the title "How to Django" or the content "Django is a great framework" articles = Article.objects.filter(Q(title='How to Django') | Q(content='Django is a great framework'))
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