SET join_algorithm = 'partial_merge';

SELECT NULL
FROM
(
    SELECT
        NULL,
        1 AS a,
        0 :: Nullable(UInt8) AS c
    UNION ALL
    SELECT
        NULL,
        65536,
        NULL
) AS js1
ALL LEFT JOIN
(
    SELECT 2 :: Nullable(UInt8) AS a
) AS js2
USING (a)
ORDER BY c
;