LeetCode（数据库）- 按日期分组销售产品

题目链接：​​​​

题目大意：略。

解题思路：解决方案(1)代码通过，但是解决方案(2)为错误代码，但是没搞明白，为啥 AC 不了。

AC 代码

-- 解决方案(1)
SELECT
    sell_date,
    COUNT(DISTINCT product) num_sold,
    GROUP_CONCAT(DISTINCT product ORDER BY product) products
FROM
    Activities
GROUP BY
    sell_date
ORDER BY
    sell_date

-- 解决方案(2)
SELECT sell_date, COUNT(*) num_sold, GROUP_CONCAT(product) products
FROM (SELECT * FROM Activities GROUP BY sell_date, product ORDER BY sell_date, product) t
GROUP BY sell_date
ORDER BY sell_date