的MySQL從一個子查詢組

Question

我有一個表logins下面的模式獲取最大計數最高計數，表中每個user_id。

我嘗試以下查詢：

SELECT MAX(num) as max_num, user_id, weekday 
FROM (
    SELECT COUNT(*) as num, user_id, weekday 
    FROM logins 
    GROUP BY user_id, weekday 
) C 
WHERE user_id = C.user_id AND num = C.num 
GROUP BY user_id; 

這讓我weekday = 1，而不是2。我認爲我不應該在這裏使用WHERE條款，但我無法設法得到正確的結果。

我檢查了，沒有運氣其他類似的問題，如：

• MYSQL, Max,Group by and Max

• Select first row in each GROUP BY group?

我創建了一個SQL撥弄我的例子：http://sqlfiddle.com/#!9/e43a71/1

Answer 1

這是上午ethod：

SELECT user_id, MAX(num) as max_num, 
     SUBSTRING_INDEX(GROUP_CONCAT(weekday ORDER BY num DESC), ',', 1) as weekday_max 
FROM (SELECT user_id, weekday, COUNT(*) as num 
     FROM logins l 
     GROUP BY user_id, weekday 
    ) uw 
GROUP BY user_id; 

Answer 2

SELECT days.user_id, days.weekday, days.num 
FROM (
    SELECT user_id, MAX(num) AS num 
    FROM (
     SELECT user_id, weekday, COUNT(*) AS num 
     FROM logins 
     GROUP BY user_id, weekday 
    ) max 
    GROUP BY user_id 
) nums 
JOIN (
    SELECT user_id, weekday, COUNT(*) as num 
    FROM logins 
    GROUP BY user_id, weekday 
) days ON(days.user_id = nums.user_id AND days.num = nums.num); 

-- With Mariadb 10.2 or MySQL 8.0.2 
WITH days AS (
    SELECT user_id, weekday, COUNT(*) as num 
    FROM logins 
    GROUP BY user_id, weekday 
) 
SELECT days.user_id, days.weekday, days.num 
FROM (
    SELECT user_id, MAX(num) AS num 
    FROM days 
    GROUP BY user_id 
) nums 
JOIN days ON(days.user_id = nums.user_id AND days.num = nums.num);