题解 | 某宝店铺连续2天及以上购物的用户及其对应的天数

需要把连续的时间抽出来，dense_rank避免了排序里同一天多次购买的计数问题

SELECT 
    user_id,
    COUNT(*) AS days_count
FROM (
    SELECT 
        user_id,
        sales_date,
        DATE_SUB(sales_date, INTERVAL DENSE_RANK() OVER (PARTITION BY user_id ORDER BY sales_date) DAY) AS date_group
    FROM (
        SELECT DISTINCT sales_date, user_id 
        FROM sales_tb
    ) t1
) t2
GROUP BY user_id, date_group
HAVING COUNT(*) >= 2
ORDER BY user_id;