SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(profile,",",-2), ",", 1) AS age,
        COUNT(device_id) AS number
FROM user_submit
GROUP BY age
ORDER BY age DESC;

我有一个问题，希望大家能解答：

  • 为什么使用COUNT(DISTINCT device_id)，就有两组案例无法通过，正常的思想不是就应该DISTINCT吗