O que dizer disso?
SELECT userid, score,
(SELECT COUNT(distinct u2.score) FROM fschema.mytab3 u2
WHERE
u2.score > u1.score) + 1 AS position FROM fschema.mytab3 u1
ORDER BY position
SELECT userid, score,
(SELECT COUNT(distinct u2.score) FROM fschema.mytab3 u2
WHERE
u2.score > u1.score) + 1 AS position FROM fschema.mytab3 u1
ORDER BY position