UPDATE
    TOTAL_SCORES AS TS
SET
    RANKING = TS_2.RK
FROM
    (SELECT
        TOTAL_SCORE
        ,RANK()OVER(ORDER BY TOTAL_SCORE DESC) AS RK
     FROM
        TOTAL_SCORES) TS_2
WHERE
    TS.TOTAL_SCORE = TS_2.TOTAL_SCORE
;