这与Asgar的查询相同，但删除了不必要的表派生-

SELECT
    `t1`.*,
    ROUND((`t1`.`count` / `t2`.`count`) * 100) `pct`
FROM `table` `t1`
JOIN `table` `t2`
    ON `t1`.`category` = `t2`.`category`
    AND `t2`.`day` = 'D1'
ORDER BY 1, 2;

这应该可以满足您要求：

SELECT
        day,
        category,
        count,
        count/(SELECT count 
                 FROM table as sub 
                   WHERE day = 'D1' 
                   AND sub.category = main.category)*100 AS pct
    FROM 
        table as main

我假设分母总是基于“D1”，并且日类别的组合总是唯一的。

这句话对你来说应该很准确：

SELECT  
main.*,  
ROUND(((main.Count/d2.Count)*100),2) 
FROM
(SELECT *   FROM day_table d1) main
  JOIN day_table d2 ON d2.Category=main.Category AND d2.Day='D1' 
  ORDER BY 
  main.Day, 
  main.Category