Class ColumnClause

lib/sqlalchemy/sql/elements.py:4905–5159

Represents a column expression from any textual string. The :class:`.ColumnClause`, a lightweight analogue to the :class:`_schema.Column` class, is typically invoked using the :func:`_expression.column` function, as in:: from sqlalchemy import column id, name = column(

class ColumnClause(
    roles.DDLReferredColumnRole,
    roles.LabeledColumnExprRole[_T],
    roles.StrAsPlainColumnRole,
    Immutable,
    NamedColumn[_T],
):
    """Represents a column expression from any textual string.

    The :class:`.ColumnClause`, a lightweight analogue to the
    :class:`_schema.Column` class, is typically invoked using the
    :func:`_expression.column` function, as in::

        from sqlalchemy import column

        id, name = column("id"), column("name")
        stmt = select(id, name).select_from("user")

    The above statement would produce SQL like:

    .. sourcecode:: sql

        SELECT id, name FROM user

    :class:`.ColumnClause` is the immediate superclass of the schema-specific
    :class:`_schema.Column` object.  While the :class:`_schema.Column`
    class has all the
    same capabilities as :class:`.ColumnClause`, the :class:`.ColumnClause`
    class is usable by itself in those cases where behavioral requirements
    are limited to simple SQL expression generation.  The object has none of
    the associations with schema-level metadata or with execution-time
    behavior that :class:`_schema.Column` does,
    so in that sense is a "lightweight"
    version of :class:`_schema.Column`.

    Full details on :class:`.ColumnClause` usage is at
    :func:`_expression.column`.

    .. seealso::

        :func:`_expression.column`

        :class:`_schema.Column`

    """

    table: Optional[FromClause]
    is_literal: bool

    __visit_name__ = "column"

    _traverse_internals: _TraverseInternalsType = [
        ("name", InternalTraversal.dp_anon_name),
        ("type", InternalTraversal.dp_type),
        ("table", InternalTraversal.dp_clauseelement),
        ("is_literal", InternalTraversal.dp_boolean),
    ]