题解 | #牛客的课程订单分析(七)#空值填充ifnull

with t as(
    select distinct user_id,
        count(id) over(partition by user_id) cnt
    from order_info
    where date>'2025-10-15'
    and status='completed'
),

t1 as(
    select o.id id,
        ifnull(c.name,'GroupBuy') source
    from order_info o
    left join client c on o.client_id=c.id
    left join t on o.user_id=t.user_id
    where date>'2025-10-15'
    and status='completed'
    and cnt>=2
    and product_name in ('C++','Python','Java')
    order by o.id
)

select 
    distinct source,
    count(id) over(partition by source) cnt
from t1

空值填充：ifnull(字段名，要填充的内容)