bigquery 引导窗口函数有没有办法使用表值作为偏移量？

Question

我想知道 bigquery 标准 sql 中的前导窗口函数是否有任何解决方法可以使用表值而不是文字或查询参数？

select 
artcl
,days
,lead(days,ofst)over(partition by artcl order by days) as tst
from(
    select 123 as artcl, 1 as days ,2 as ofst
    union all
    select 123 as artcl, 2 as days ,2 as ofst
    union all
    select 123 as artcl, 3 as days ,2 as ofst
)

Answer 1

您可以使用以下方法

select artcl, days, ofst,
  arr[safe_offset(row_number() over(partition by artcl order by days) + ofst - 1)] as tst
from `project.dataset.table`
join (
  select artcl, array_agg(days order by days) arr, 
  from `project.dataset.table`
  group by artcl
)
using(artcl)