我有一张table

student class score
--------------------
A        1       6
B        1       5
C        2       6

我想用sql计算每个类的分数与所有类的平均分数的偏差百分比；换句话说

(avg_score_in_one_class- avg_score_all_classes)/avg_score_all_classes *100

我使用这个查询用sql计算了它

SELECT 
class, 
(AVG(score) - (SELECT AVG(score) FROM table))
/
(SELECT AVG(score) FROM table)

* 100

FROM table
GROUP BY class

结果应该是

class deviation
---------------
1      -2.9411764705882404
2      5.882352941176465

有没有办法写得更好？例如，我在想一个例子，你有很多分数列。
根据gordon linoff的建议，我找到了部分解决方案：

WITH temp_table as 
(
    SELECT
        class,
    AVG(score) OVER (PARTITION by class) as avg_class,
    AVG(score) OVER () as avg_score
    FROM table
)

SELECT
    class,
AVG((avg_class-avg_score)/avg_score*100.0) as dev
FROM temp_table
GROUP BY class;

但要将其推广到多个分数列仍然不容易。