嵌套 window 函数在雪花中不起作用

Question

我正在研究将 spark sql 迁移到 snowsql。有一次我遇到了一个场景，我在 spark sql 中使用了嵌套的 window 函数。我想将该 sql 查询迁移到雪花中。但是雪花不支持嵌套 window 函数。

Spark sql 查询 -

SELECT 
    *,
    (case when (
        (
            lead(timestamp -lag(timestamp)
                over (partition by session_id order by timestamp))
                over (partition by session_id order by timestamp)
        ) is not null)
     then  
    (
        lead(timestamp -lag(timestamp)
            over (partition by session_id order by timestamp))
            over (partition by session_id order by timestamp)
    ) 
    else 0 end)/1000 as pg_to_pg
FROM dwell_time_step2

输出- 我已尝试将上述查询转换为如下雪花。

化雪sql -

with lagsession as (
SELECT 
    a.*,
    lag(timestamp) over (partition BY session_id   order by timestamp asc) lagsession 
FROM mktg_web_wi.dwell_time_step2 a
)

select 
    a.,
    nvl(lead(a.timestamp - b.lagsession) over (partition BY a.session_id order by   a.timestamp),0)/1000 pg_to_pg
FROM mktg_web_wi.dwell_time_step2 a,
    lagsession b
WHERE a.key=b.key
order by timestamp;

输出-

这里，问题出在 Snow-sql 输出中。驻留时间值正在分配给不同的网址。

期望使 spark-sql 查询在雪上工作sql 并且两种情况下的输出应该相同。

如果有人知道如何解决这个问题，请告诉我。

谢谢！！

Answer 1

我认为将其从嵌套 window 函数更改为 cte 已经改变了滞后和超前所指的记录，但我很难理解这一点。

无论如何，如果我能理解您的代码，我认为有一种更简单的方法，只有一个 windows 函数。

select 
    a.*,
    (nvl(lead(a.timestamp) over (partition BY a.session_id order by a.timestamp) - a.timestamp)/1000,0) pg_to_pg
FROM mktg_web_wi.dwell_time_step2 a
order by timestamp;

嵌套 window 函数在雪花中不起作用

Nested window function not working in snowflake

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snowflake-cloud-data-platform

snowsql