Method one_or_none

lib/sqlalchemy/orm/query.py:2768–2792

Return at most one result or raise an exception. Returns ``None`` if the query selects no rows. Raises ``sqlalchemy.orm.exc.MultipleResultsFound`` if multiple object identities are returned, or if multiple rows are returned for a query that returns only scalar value

(self)

            return self.limit(1)._iter().first()  # type: ignore

    def one_or_none(self) -> Optional[_T]:
        """Return at most one result or raise an exception.

        Returns ``None`` if the query selects
        no rows.  Raises ``sqlalchemy.orm.exc.MultipleResultsFound``
        if multiple object identities are returned, or if multiple
        rows are returned for a query that returns only scalar values
        as opposed to full identity-mapped entities.

        Calling :meth:`_query.Query.one_or_none`
        results in an execution of the
        underlying query.

        .. seealso::

            :meth:`_query.Query.first`

            :meth:`_query.Query.one`

            :meth:`_engine.Result.one_or_none` - v2 comparable method.

            :meth:`_engine.Result.scalar_one_or_none` - v2 comparable method.

        """
        return self._iter().one_or_none()  # type: ignore

    def one(self) -> _T:
        """Return exactly one result or raise an exception.