题解 | #牛客的课程订单分析(六)#

第一版答案 总结：输出正确，但代码有重复（冗余），需要改进。

SELECT o.id,
o.is_group_buy,
case
    when is_group_buy='No' then c.name
    when is_group_buy='Yes' then NULL
end client_name
FROM order_info o
LEFT JOIN client c
ON o.client_id=c.id
WHERE o.user_id in (
    select user_id from order_info
    where date>'2025-10-10'
    and product_name IN('C++','Java','Python')
    and status='completed'
    GROUP BY user_id
    having count(id)>=2
)
and date>'2025-10-10'    #此段代码重复
    and product_name IN('C++','Java','Python')
    and status='completed'
order by o.id asc