sql - 在 BigQuery 中使用 LEAD

Question

假设我的表结构是这样的

我计划按（USER 和 SEQUENCE）对它进行分组，并获取下一个序列的 LEAD 时间戳。这是我正在寻找的输出

如果可能的话，我可以在不使用 LEAD 函数的情况下解决这个问题吗？

Answer 1

以下是 BigQuery 标准 SQL

我将展示两个选项 - 使用 JOIN（只是为了证明我正确理解/反向工程预期逻辑），然后是无 JOIN 版本（注意我使用ts的是字段名称而不是timestamp）

使用 JOIN

#standardSQL
SELECT a.user, a.sequence, MIN(b.ts) ts 
FROM (
  SELECT user, sequence, MAX(ts) AS max_ts
  FROM `project.dataset.table`
  GROUP BY user, sequence
) a
LEFT JOIN `project.dataset.table` b
ON a.user = b.user AND b.sequence = a.sequence + 1
WHERE a.max_ts <= IFNULL(b.ts, a.max_ts)
GROUP BY user, sequence
-- ORDER BY user, sequence

无JOIN版本

#standardSQL
SELECT
  user, sequence, 
  (
    SELECT ts FROM UNNEST(arr_ts) ts 
    WHERE max_ts < ts ORDER BY ts LIMIT 1
  ) ts
FROM (
  SELECT
    user, sequence, max_ts,
    LEAD(arr_ts) OVER (PARTITION BY user ORDER BY sequence) arr_ts
  FROM (
  SELECT 
      user, sequence, MAX(ts) max_ts, 
      ARRAY_AGG(ts ORDER BY ts) arr_ts
    FROM `project.dataset.table`
    GROUP BY user, sequence
  )
)
-- ORDER BY user, sequence   

以上两个版本都可以使用以下虚拟数据进行测试/播放

WITH `project.dataset.table` AS (
  SELECT 'user1' user, 2 sequence, 'T1' ts UNION ALL
  SELECT 'user1', 2, 'T2' UNION ALL
  SELECT 'user1', 1, 'T3' UNION ALL
  SELECT 'user1', 1, 'T4' UNION ALL
  SELECT 'user1', 3, 'T5' UNION ALL
  SELECT 'user1', 2, 'T6' UNION ALL
  SELECT 'user1', 3, 'T7' UNION ALL
  SELECT 'user1', 3, 'T8' 
)   

并且都返回低于结果

user    sequence    ts   
user1   1           T6   
user1   2           T7   
user1   3           null     

Answer 2

不确定 bigquery，但在一般 SQL 中，它会写成：

select user, sequence, LEAD (max_timestamp,1) OVER (PARTITION BY user ORDER BY sequence) as timestamp
from (
    select user, sequence, max(timestamp) as max_timestamp
    from table
    group by user, sequence) q1;

请注意保留字，例如表、用户、时间戳等。

编辑：是的，忘记这个答案，对所需的输出不够关注。米哈伊尔做对了！