Function tablesample

lib/sqlalchemy/sql/_selectable_constructors.py:640–687

Return a :class:`_expression.TableSample` object. :class:`_expression.TableSample` is an :class:`_expression.Alias` subclass that represents a table with the TABLESAMPLE clause applied to it. :func:`_expression.tablesample` is also available from the :class:`_expression.FromClau

(
    selectable: _FromClauseArgument,
    sampling: Union[float, Function[Any]],
    name: Optional[str] = None,
    seed: Optional[roles.ExpressionElementRole[Any]] = None,
)

def tablesample(
    selectable: _FromClauseArgument,
    sampling: Union[float, Function[Any]],
    name: Optional[str] = None,
    seed: Optional[roles.ExpressionElementRole[Any]] = None,
) -> TableSample:
    """Return a :class:`_expression.TableSample` object.

    :class:`_expression.TableSample` is an :class:`_expression.Alias`
    subclass that represents
    a table with the TABLESAMPLE clause applied to it.
    :func:`_expression.tablesample`
    is also available from the :class:`_expression.FromClause`
    class via the
    :meth:`_expression.FromClause.tablesample` method.

    The TABLESAMPLE clause allows selecting a randomly selected approximate
    percentage of rows from a table. It supports multiple sampling methods,
    most commonly BERNOULLI and SYSTEM.

    e.g.::

        from sqlalchemy import func

        selectable = people.tablesample(
            func.bernoulli(1), name="alias", seed=func.random()
        )
        stmt = select(selectable.c.people_id)

    Assuming ``people`` with a column ``people_id``, the above
    statement would render as:

    .. sourcecode:: sql

        SELECT alias.people_id FROM
        people AS alias TABLESAMPLE bernoulli(:bernoulli_1)
        REPEATABLE (random())

    :param sampling: a ``float`` percentage between 0 and 100 or
        :class:`_functions.Function`.

    :param name: optional alias name

    :param seed: any real-valued SQL expression.  When specified, the
     REPEATABLE sub-clause is also rendered.

    """
    return TableSample._factory(selectable, sampling, name=name, seed=seed)


@overload