aggregate()
Terminal clause returning a dictionary of computed aggregate values over a QuerySet.
Aggregate functions
Avg, Max, Min, Count and other functions from django.db.models.
annotate()
Generates an aggregate for each item in a QuerySet as an attribute.
atomic()
Create a block of code guaranteeing atomicity; usable as decorator or context manager, nestable.
ATOMIC_REQUESTS
Wraps each request in a transaction; commits on success, rolls back on exception.
bulk_create() and bulk_update()
Create or update many rows in bulk.
Cast ¶
Coalesce ¶
Collate ¶
Comparison and conversion functions ¶
Database Functions ¶
Date functions ¶
DateField extracts ¶
DateTimeField extracts ¶
default argument
Provide a default returned instead of None when no rows exist.
defer() and only()
Control which fields are loaded from the database.
connection.execute_wrapper()
Returns a context manager that installs a wrapper around database query executions on the thread-local connection.
QuerySet.explain()
Shows how the database executes a query, including indexes and joins.
Extract ¶
F() expressions and annotate()
Do filtering and aggregation work in the database.
Filtered aggregates
Count with filter=Q(...) to aggregate a subset of related rows.
Fixtures
Greatest ¶
QuerySet.iterator()
Reduces memory use when iterating over many objects.
Least ¶
Making queries
Managers
Many-to-many relationships
Model relationship API usage examples for many-to-many relationships.
Many-to-one relationships
Model relationship API usage examples for many-to-one relationships.
Models
A model is the single, definitive source of information about your data.
non_atomic_requests()
Decorator that negates the effect of ATOMIC_REQUESTS for a given view.
NullIf ¶
One-to-one relationships
Model relationship API usage examples for one-to-one relationships.
RawSQL and raw SQL
Add explicit SQL to queries when ORM expressions are insufficient.
select_related() and prefetch_related()
Efficiently retrieve related objects in fewer queries.
Tablespaces
values() and values_list()
Retrieve only needed fields instead of full model instances.
Wrapper parameters
Wrappers receive execute, sql, params, many, and context arguments for each query execution.