1. 先利用窗口函数计算出符合条件的用户购买数
    select *, count(*) over(partition by user_id) as cnt from order_info
where date > '2025-10-15'
and product_name in ('C++','Java','Python')
and status = 'completed'
  2. 再利用外联结将两个表联结，注意组团（YES）的标识为0，不在client表内，联结后的值为空值，符合题目要求。
    select a.id, a.is_group_buy, b.name as client_name from 
(select *, count(*) over(partition by user_id) as cnt from order_info
where date > '2025-10-15'
and product_name in ('C++','Java','Python')
and status = 'completed') a left join client b on a.client_id = b.id
where a.cnt >= 2
order by a.id asc;