SET @r = 0;
SET @l = 0;
SET @s = 1;
UPDATE `数据表` SET `名次列` = (
CASE
WHEN `排名值列` = @l THEN @r := @r + (@s := @s + 1) - @s
ELSE @r := (@r + @s) + (@s := 1) - 1 END)
WHERE 1 
ORDER BY `排名值列` DESC

可以实现并列排名，名次值类似：1,2,3,3,3,6,6,8……