mySQL/ MariaDB 使用变量计算

问：

我想让DB计算出最受欢迎的书。我的数据库查询有效，但是不正确。显然是因为排序为时已晚。如何针对mariaDB 10.3进行改进？calculated_pointscounter

获得 10 分的预订应获得第 1 名。

获得 8 分的预订应获得第 2 名。

获得 4 分的预订应获得第 3 名。

SET @var = 0;
SELECT 
   (@var:=@var+1) AS counter, 
   (row1 * row2 / 4) as calculated_points 
from bookz 
WHERE kat = '6' 
  AND pubdate > DATE_SUB(CURDATE(), INTERVAL 12 MONTH) 
  AND pub = '1' 
  AND ratings > '1' 
  AND productType = 'pbook' 
GROUP BY title 
ORDER BY calculated_points desc 
LIMIT 256