mysql 分数排名,更新表

如何用mysql 查询出数据出数据排名,然后加编号;

表字段说明:查询e_Task_Result表 ,score代表分数,task_result_id 代表id

SELECT
(@rowNO := @rowNo+1) AS rowno,
task_result_id ,score FROM (
(SELECT task_result_id ,score FROM e_task_result ORDER BY score DESC) a,(SELECT @rowNo :=0) b )

如何将查询出来的排名更新到表中
表字段说明:查询e_Task_Result表 ,score代表分数,task_result_id 代表id,rank代表排名

UPDATE e_task_result d
LEFT JOIN (SELECT
(@rowNO := @rowNo+1) AS rowno,
task_result_id
FROM (SELECT
task_result_id
FROM e_task_result etr
ORDER BY task_result_status DESC,etr.score DESC,end_date) a,
(SELECT
@rowNO :=0) b) c
ON c.task_Result_id = d.task_result_id
SET d.rank = rowno