Question

我正在使用Bigquery，因此我需要使用ROW_NUMBER（）才能仅获取符合某些条件的第一行。

示例：

select *except(rn)
from (
SELECT
  *,
  ROW_NUMBER() OVER (PARTITION BY id order by timedate desc) AS rn
FROM
 table
)
where rn = 1

但是，查询将因为表太大而失败。如何应用这种逻辑而又不会耗尽资源？

Answer 1

以下是用于BigQuery标准SQL

#standardSQL
SELECT AS VALUE ARRAY_AGG(t ORDER BY timedate DESC LIMIT 1)[OFFSET(0)]
FROM `project.dataset.table` t
GROUP BY id

您可以测试以下虚拟数据并在其上播放

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 1 id, 2 timedate, 3 z UNION ALL
  SELECT 1,4,5 UNION ALL
  SELECT 1,6,7 UNION ALL
  SELECT 2,8,9 UNION ALL
  SELECT 2, 10, 11
)
SELECT AS VALUE ARRAY_AGG(t ORDER BY timedate DESC LIMIT 1)[OFFSET(0)]
FROM `project.dataset.table` t
GROUP BY id

结果是

Row id  timedate    z    
1   1   6           7    
2   2   10          11

表太大时ROW_NUMBER（）失败

1 个答案: