QuerySets are lazy, meaning they are not evaluated until you explicitly request the data. This allows for efficient chaining of filters and other operations without hitting the database multiple times.
# No database query yet
authors = Author.objects.all()
# Database query happens here
for author in authors:
print(author.name)
all()Returns all objects in the QuerySet.
authors = Author.objects.all()
filter()Returns a new QuerySet containing objects that match the given lookup parameters.
authors_named_john = Author.objects.filter(name='John')
exclude()Returns a new QuerySet containing objects that do not match the given lookup parameters.
authors_not_named_john = Author.objects.exclude(name='John')
order_by()Returns a new QuerySet ordered by the given field(s).
authors_ordered_by_name = Author.objects.order_by('name')
distinct()Returns a new QuerySet with duplicate records removed.
distinct_authors = Author.objects.distinct()
values()Returns a QuerySet that returns dictionaries, rather than model instances, when iterated over.
author_names = Author.objects.values('name')
values_list()Similar to values(), but returns tuples instead of dictionaries.
author_names = Author.objects.values_list('name', flat=True)
count()Returns the number of objects in the QuerySet.
author_count = Author.objects.count()
exists()Returns True if the QuerySet contains any results, otherwise False.
has_authors = Author.objects.exists()
You can use Python’s array-slicing syntax to limit QuerySets.
first_ten_authors = Author.objects.all()[:10]