django.db.models.expressions.Subquery

class documentation

class Subquery(BaseExpression, Combinable):

Known subclasses: django.db.models.expressions.Exists

An explicit subquery. It may contain OuterRef() references to the outer query which will be resolved when it is applied to that query.

Method	`__init__`	Undocumented
Method	`_resolve_output_field`	Attempt to infer the output type of the expression. If the output fields of all source fields match then, simply infer the same type here. This isn't always correct, but it makes sense most of the time.
Method	`as_sql`	Responsible for returning a (sql, [params]) tuple to be included in the current query.
Method	`copy`	Undocumented
Method	`get_external_cols`	Undocumented
Method	`get_group_by_cols`	Undocumented
Method	`get_source_expressions`	Undocumented
Method	`set_source_expressions`	Undocumented
Class Variable	`contains_aggregate`	Undocumented
Class Variable	`empty_result_set_value`	Undocumented
Class Variable	`template`	Undocumented
Instance Variable	`extra`	Undocumented
Instance Variable	`query`	Undocumented
Property	`external_aliases`	Undocumented

Inherited from BaseExpression:

Static Method	`_convert_value_noop`	Undocumented
Method	`__getstate__`	Undocumented
Method	`_parse_expressions`	Undocumented
Method	`asc`	Undocumented
Method	`desc`	Undocumented
Method	`flatten`	Recursively yield this expression and all subexpressions, in depth-first order.
Method	`get_db_converters`	Undocumented
Method	`get_lookup`	Undocumented
Method	`get_source_fields`	Return the underlying field types used by this aggregate.
Method	`get_transform`	Undocumented
Method	`relabeled_clone`	Undocumented
Method	`resolve_expression`	Provide the chance to do any preprocessing or validation before being added to the query.
Method	`reverse_ordering`	Undocumented
Method	`select_format`	Custom format for select clauses. For example, EXISTS expressions need to be wrapped in CASE WHEN on Oracle.
Class Variable	`_output_field_resolved_to_none`	Undocumented
Class Variable	`filterable`	Undocumented
Class Variable	`is_summary`	Undocumented
Class Variable	`window_compatible`	Undocumented
Property	`_output_field_or_none`	Return the output field of this expression, or None if _resolve_output_field() didn't return an output type.
Property	`conditional`	Undocumented
Property	`contains_column_references`	Undocumented
Property	`contains_over_clause`	Undocumented
Property	`convert_value`	Expressions provide their own converters because users have the option of manually specifying the output_field which may be a different type from the one the database returns.
Property	`field`	Undocumented
Property	`output_field`	Return the output type of this expressions.

Inherited from Combinable:

Constant	`ADD`	Undocumented
Constant	`BITAND`	Undocumented
Constant	`BITLEFTSHIFT`	Undocumented
Constant	`BITOR`	Undocumented
Constant	`BITRIGHTSHIFT`	Undocumented
Constant	`BITXOR`	Undocumented
Constant	`DIV`	Undocumented
Constant	`MOD`	Undocumented
Constant	`MUL`	Undocumented
Constant	`POW`	Undocumented
Constant	`SUB`	Undocumented
Method	`__add__`	Undocumented
Method	`__and__`	Undocumented
Method	`__mod__`	Undocumented
Method	`__mul__`	Undocumented
Method	`__neg__`	Undocumented
Method	`__or__`	Undocumented
Method	`__pow__`	Undocumented
Method	`__radd__`	Undocumented
Method	`__rand__`	Undocumented
Method	`__rmod__`	Undocumented
Method	`__rmul__`	Undocumented
Method	`__ror__`	Undocumented
Method	`__rpow__`	Undocumented
Method	`__rsub__`	Undocumented
Method	`__rtruediv__`	Undocumented
Method	`__sub__`	Undocumented
Method	`__truediv__`	Undocumented
Method	`_combine`	Undocumented
Method	`bitand`	Undocumented
Method	`bitleftshift`	Undocumented
Method	`bitor`	Undocumented
Method	`bitrightshift`	Undocumented
Method	`bitxor`	Undocumented

def __init__(self, queryset, output_field=None, **extra):

overrides django.db.models.expressions.BaseExpression.__init__

overridden in django.db.models.expressions.Exists

Undocumented

def _resolve_output_field(self):

overrides django.db.models.expressions.BaseExpression._resolve_output_field

Attempt to infer the output type of the expression. If the output fields of all source fields match then, simply infer the same type here. This isn't always correct, but it makes sense most of the time.

Consider the difference between 2 + 2 and 2 / 3. Inferring the type here is a convenience for the common case. The user should supply their own output_field with more complex computations.

If a source's output field resolves to None, exclude it from this check. If all sources are None, then an error is raised higher up the stack in the output_field property.

def as_sql(self, compiler, connection, template=None, query=None, **extra_context):

overrides django.db.models.expressions.BaseExpression.as_sql

overridden in django.db.models.expressions.Exists

Responsible for returning a (sql, [params]) tuple to be included in the current query.

Different backends can provide their own implementation, by providing an as_{vendor} method and patching the Expression:

``` def override_as_sql(self, compiler, connection):

# custom logic return super().as_sql(compiler, connection)

setattr(Expression, 'as_' + connection.vendor, override_as_sql) ```

Arguments:

compiler: the query compiler responsible for generating the query. Must have a compile method, returning a (sql, [params]) tuple. Calling compiler(value) will return a quoted value.
connection: the database connection used for the current query.

Return: (sql, params)

Where sql is a string containing ordered sql parameters to be replaced with the elements of the list params.

def copy(self):

overrides django.db.models.expressions.BaseExpression.copy

Undocumented

def get_external_cols(self):

Undocumented

def get_group_by_cols(self, alias=None):

overrides django.db.models.expressions.BaseExpression.get_group_by_cols

Undocumented

def get_source_expressions(self):

overrides django.db.models.expressions.BaseExpression.get_source_expressions

Undocumented

def set_source_expressions(self, exprs):

overrides django.db.models.expressions.BaseExpression.set_source_expressions

Undocumented

contains_aggregate: bool =

overrides django.db.models.expressions.BaseExpression.contains_aggregate

Undocumented

empty_result_set_value =

Undocumented

template: str =

overridden in django.db.models.expressions.Exists

Undocumented

extra =

Undocumented

query =

Undocumented

@property
external_aliases =

Undocumented