Question

我试图从基于时间戳的值列中提取第一个非空值。有人可以分享你对此的看法。谢谢。

到目前为止我尝试了什么？

rake routes

FIRST_VALUE( column ) OVER ( PARTITION BY id ORDER BY timestamp)

Input :-

Answer 1

尝试这个字符串操作的老技巧：

Select 
ID,
  Column,
  ttimestamp,
  LTRIM(Right(CColumn,20)) as CColumn,
  FROM
(SELECT
  ID,
  Column,
  ttimestamp,
  MIN(Concat(RPAD(IF(Column is null, '9999999999999999',STRING(ttimestamp)),20,'0'),LPAD(Column,20,' '))) OVER (Partition by ID) CColumn
FROM (

  SELECT
    *
  FROM (Select 1 as ID, STRING(NULL) as Column, 0.4375 as ttimestamp),
        (Select 1 as ID, STRING(NULL) as Column, 0.438194444444444 as ttimestamp),
        (Select 1 as ID, 'xyz' as Column, 0.438888888888889 as ttimestamp),
        (Select 1 as ID, 'def' as Column, 0.439583333333333 as ttimestamp),
        (Select 2 as ID, STRING(NULL) as Column, 0.479166666666667 as ttimestamp),
        (Select 2 as ID, 'abc' as Column, 0.479861111111111 as ttimestamp)
))

Answer 2

您可以像这样修改您的sql以获取所需的数据。

FIRST_VALUE( column )
  OVER ( 
    PARTITION BY id
    ORDER BY
      CASE WHEN column IS NULL then 0 ELSE 1 END DESC,
      timestamp
  )

Answer 3

据我所知，Big Query没有像'IGNORE NULLS'或'NULLS LAST'这样的选项。鉴于此，这是我能想到的最简单的解决方案。我希望看到更简单的解决方案。假设输入数据在表“original_data”中，

select w2.id, w1.column, w2.timestamp
from
(select id,column,timestamp
   from
     (select id,column,timestamp, row_number() 
                   over (partition BY id ORDER BY timestamp) position
       FROM original_data
       where column is not null
    )
   where position=1 
) w1
right outer join
 original_data as w2
on w1.id = w2.id

Answer 4

SELECT id，
（SELECT top（1）column FROM test1 where id = 1且column is auto order by autoID desc）作为名称，时间戳来自你的表

输出： - 1，＆＃39; xyz＆＃39;，上午10:30 1，＆＃39; xyz＆＃39;，上午10:31 1，＆＃39; xyz＆＃39;，上午10:32 1，＆＃39; xyz＆＃39;，上午10:33 2，＆＃39; abc＆＃39;，11：30 am 2，＆＃39; abc＆＃39;，11：31 am

如何从Big Query中的值列中获取第一个not null值？

4 个答案: