雪花 window 函数 last_value 和最大值

Question

我有一个这样的 table :

我想为每个 user_key 获取每个日期/月/工作日/周的顶部 total_listened

我想我需要使用 window 功能我可以获得不同的日期格式：

MONTH(stream_date) for months
WEEKDAY(stream_date) for weekday
WEEK(stream_date) for week

我试过这个：

select 
MAX(vals.total_listened_per_day) as RECORD_STREAM_DAY_TIME,
MAX(vals.total_listened_per_month) as RECORD_STREAM_MONTH_TIME,
MAX(vals.total_listened_per_week) as RECORD_STREAM_WEEK_TIME,
MAX(vals.most_active_weekday) as MOST_ACTIVE_WEEKDAY_TIME
 last_value(days.date) over (partition by user_key order by days.total_listened) as RECORD_STREAMDAY,
from
(
select user_key, stream_date as date,
sum(st.length_listened) over (partition by user_key, stream_date) as total_listened_per_day,
sum(st.length_listened) over (partition by user_key, MONTH(stream_date)) as total_listened_per_month,
sum(st.length_listened) over (partition by user_key, WEEK(stream_date)) as total_listened_per_week,
sum(st.length_listened) over (partition by user_key, DAYNAME(stream_date)) as most_active_weekday
group by 1,2
 .....
 )

用于获取金额（以 _TIME 结尾的变量），但不适用于获取特定日期/月份....（末尾没有 _TIME 的变量，例如 RECORD_STREAMDAY) ，这是因为 group by ，它按 stream_date 而不是 month(stream_date) 分组，例如，我不知道如果没有每个 [=15 的 doin 子查询我怎么能做到这一点=]

Answer 1

我觉得你想要的逻辑是：

select user_key,
    max(total_listened_per_day  ) as max_total_listened_per_day
    max(total_listened_per_week ) as max_total_listened_per_week,
    max(total_listened_per_month) as max_total_listened_per_month,
    max(case when rn_day   = 1 then date_trunc('day',   stream_date) end) as most_active_day,
    max(case when rn_week  = 1 then date_trunc('week',  stream_date) end) as most_active_week,
    max(case when rn_month = 1 then date_trunc('month', stream_date) end) as most_active_month
from (  
    select t.*,
        rank() over(partition by user_key order by total_listened_per_day   desc) as rn_day,
        rank() over(partition by user_key order by total_listened_per_week  desc) as rn_week,
        rank() over(partition by user_key order by total_listened_per_month desc) as rn_month
    from (
        select t.*
            sum(st.length_listened) over (partition by user_key, date_trunc('day',   stream_date)) as total_listened_per_day,
            sum(st.length_listened) over (partition by user_key, date_trunc('week',  stream_date)) as total_listened_per_week
            sum(st.length_listened) over (partition by user_key, date_trunc('month', stream_date)) as total_listened_per_month
        from mytable t
    ) t
) t
group by user_key

最内层子查询计算每天、每周和每月收听时间的window总和。下一个子查询使用该信息对记录进行排名。最后，外层查询使用条件聚合，带上对应的durations和periods。如果有联系，则选择最近的时期。

雪花 window 函数 last_value 和最大值

Snowflake window function last_value and max

sql

datetime

greatest-n-per-group

window-functions

snowflake-cloud-data-platform