Module « sqlalchemy »

Fonction func - module sqlalchemy

Signature de la fonction func

def func(*c, **kwargs) 

Description

func.__doc__

Generate SQL function expressions.

    :data:`.func` is a special object instance which generates SQL
    functions based on name-based attributes, e.g.::

        >>> print(func.count(1))
        count(:param_1)

    The returned object is an instance of :class:`.Function`, and  is a
    column-oriented SQL element like any other, and is used in that way::

        >>> print(select(func.count(table.c.id)))
        SELECT count(sometable.id) FROM sometable

    Any name can be given to :data:`.func`. If the function name is unknown to
    SQLAlchemy, it will be rendered exactly as is. For common SQL functions
    which SQLAlchemy is aware of, the name may be interpreted as a *generic
    function* which will be compiled appropriately to the target database::

        >>> print(func.current_timestamp())
        CURRENT_TIMESTAMP

    To call functions which are present in dot-separated packages,
    specify them in the same manner::

        >>> print(func.stats.yield_curve(5, 10))
        stats.yield_curve(:yield_curve_1, :yield_curve_2)

    SQLAlchemy can be made aware of the return type of functions to enable
    type-specific lexical and result-based behavior. For example, to ensure
    that a string-based function returns a Unicode value and is similarly
    treated as a string in expressions, specify
    :class:`~sqlalchemy.types.Unicode` as the type:

        >>> print(func.my_string(u'hi', type_=Unicode) + ' ' +
        ...       func.my_string(u'there', type_=Unicode))
        my_string(:my_string_1) || :my_string_2 || my_string(:my_string_3)

    The object returned by a :data:`.func` call is usually an instance of
    :class:`.Function`.
    This object meets the "column" interface, including comparison and labeling
    functions.  The object can also be passed the :meth:`~.Connectable.execute`
    method of a :class:`_engine.Connection` or :class:`_engine.Engine`,
    where it will be
    wrapped inside of a SELECT statement first::

        print(connection.execute(func.current_timestamp()).scalar())

    In a few exception cases, the :data:`.func` accessor
    will redirect a name to a built-in expression such as :func:`.cast`
    or :func:`.extract`, as these names have well-known meaning
    but are not exactly the same as "functions" from a SQLAlchemy
    perspective.

    Functions which are interpreted as "generic" functions know how to
    calculate their return type automatically. For a listing of known generic
    functions, see :ref:`generic_functions`.

    .. note::

        The :data:`.func` construct has only limited support for calling
        standalone "stored procedures", especially those with special
        parameterization concerns.

        See the section :ref:`stored_procedures` for details on how to use
        the DBAPI-level ``callproc()`` method for fully traditional stored
        procedures.

    .. seealso::

        :ref:`coretutorial_functions` - in the Core Tutorial

        :class:`.Function`