题解 | #牛客的课程订单分析(四)#

with t1 as (
    select user_id, count(*) as cnt from (select * from order_info where
    (product_name = 'C++' OR product_name = 'Java' or product_name = 'Python') and date > '2025-10-15' and status = 'completed') t
    group by user_id
    having count(*) >= 2
),
t2 as (
    select user_id, min(date) as first_buy_date
    from order_info
    where (product_name = 'C++' OR product_name = 'Java' or product_name = 'Python') and date > '2025-10-15' and status = 'completed'
    group by user_id
)

select t1.user_id, first_buy_date, cnt from t1 inner join t2 using(user_id)
order by user_id

聚合函数最好还是和 group by连用，刚才是count，现在是min，还有max也是