MySQL - Get the max count from a subquery group - mysql

Question

I have a table logins with the following schema:
| id | user_id | weekday |
|----|---------|---------|
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 1 | 2 |
...
Weekday is a number from 0 to 6.
I want to get which weekday has the highest count, for each user_id in the table.
I tried the following query:
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;
Which gets me weekday = 1 instead of 2. I think that I shouldn't use a WHERE clause here, but I couldn't manage to get the correct result.
I've checked other similar questions with no luck, such as:
MYSQL, Max,Group by and Max
Select first row in each GROUP BY group?
I created a SQL Fiddle with my example: http://sqlfiddle.com/#!9/e43a71/1

Answer 1

Here is a method:
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);