使用mysql 8可以使用窗口函数

WITH
  cte AS  (SELECT votedRestaurant, WEEK, COUNT(*) total
            FROM votes 
            GROUP BY votedRestaurant,WEEK 
            ORDER BY WEEK DESC, votedRestaurant)
SELECT *
FROM (
SELECT *,
    row_number() over (PARTITION BY WEEK ORDER BY total DESC) AS rn
FROM 
    cte
 ) t
WHERE rn = 1

演示
另一种方法是使用字符串函数

SELECT t.week, SUBSTRING_INDEX(GROUP_CONCAT(t.votedRestaurant ORDER BY t.total DESC),',',1) votedRestaurant, MAX(t.total)
FROM(
    SELECT votedRestaurant, WEEK, COUNT(*)  total
    FROM votes 
    GROUP BY votedRestaurant,WEEK 
    ORDER BY WEEK DESC
) t
GROUP BY t.week
ORDER BY t.week DESC

演示

例如，您可以尝试使用limit和按计数排序

SELECT votedRestaurant,
           week,
           COUNT(*) AS tcount
    FROM mylunch.votes
    GROUP BY votedRestaurant,
             week
    ORDER BY tcount DESC
    LIMIT 1;

此外，您还可以使用子查询，如文档所述。