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Module « sqlalchemy »

Fonction over - module sqlalchemy

Signature de la fonction over

def over(element: 'FunctionElement[_T]', partition_by: 'Optional[_ByArgument]' = None, order_by: 'Optional[_ByArgument]' = None, range_: 'Optional[typing_Tuple[Optional[int], Optional[int]]]' = None, rows: 'Optional[typing_Tuple[Optional[int], Optional[int]]]' = None) -> 'Over[_T]' 

Description

help(sqlalchemy.over)

Produce an :class:`.Over` object against a function.

Used against aggregate or so-called "window" functions,
for database backends that support window functions.

:func:`_expression.over` is usually called using
the :meth:`.FunctionElement.over` method, e.g.::

    func.row_number().over(order_by=mytable.c.some_column)

Would produce:

.. sourcecode:: sql

    ROW_NUMBER() OVER(ORDER BY some_column)

Ranges are also possible using the :paramref:`.expression.over.range_`
and :paramref:`.expression.over.rows` parameters.  These
mutually-exclusive parameters each accept a 2-tuple, which contains
a combination of integers and None::

    func.row_number().over(order_by=my_table.c.some_column, range_=(None, 0))

The above would produce:

.. sourcecode:: sql

    ROW_NUMBER() OVER(ORDER BY some_column
    RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

A value of ``None`` indicates "unbounded", a
value of zero indicates "current row", and negative / positive
integers indicate "preceding" and "following":

* RANGE BETWEEN 5 PRECEDING AND 10 FOLLOWING::

    func.row_number().over(order_by="x", range_=(-5, 10))

* ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW::

    func.row_number().over(order_by="x", rows=(None, 0))

* RANGE BETWEEN 2 PRECEDING AND UNBOUNDED FOLLOWING::

    func.row_number().over(order_by="x", range_=(-2, None))

* RANGE BETWEEN 1 FOLLOWING AND 3 FOLLOWING::

    func.row_number().over(order_by="x", range_=(1, 3))

:param element: a :class:`.FunctionElement`, :class:`.WithinGroup`,
 or other compatible construct.
:param partition_by: a column element or string, or a list
 of such, that will be used as the PARTITION BY clause
 of the OVER construct.
:param order_by: a column element or string, or a list
 of such, that will be used as the ORDER BY clause
 of the OVER construct.
:param range\_: optional range clause for the window.  This is a
 tuple value which can contain integer values or ``None``,
 and will render a RANGE BETWEEN PRECEDING / FOLLOWING clause.

:param rows: optional rows clause for the window.  This is a tuple
 value which can contain integer values or None, and will render
 a ROWS BETWEEN PRECEDING / FOLLOWING clause.

This function is also available from the :data:`~.expression.func`
construct itself via the :meth:`.FunctionElement.over` method.

.. seealso::

    :ref:`tutorial_window_functions` - in the :ref:`unified_tutorial`

    :data:`.expression.func`

    :func:`_expression.within_group`

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