题解 | #牛客的课程订单分析(七)#

思路：先筛数据形成tb1，再找出购买≥2次的人所对应的数据形成tb2, 最后将name里null的部分换成GroupBuy即可。
with tb1 as(
    select user_id, name from order_info left join client on order_info.client_id=client.id
    where date>'2025-10-15' and status='completed' and product_name in ('C++','Java','Python')
)

select 
case when name is null then 'GroupBuy' else name end as source, cnt
from(
select name, count(if(name is null, 1, name)) as cnt
from tb1
where user_id in 
(select user_id from tb1 group by user_id having count(user_id)>=2)
group by name) tb2
order by source