BigQuery：计算每个人在时间窗口内的聚合

Question

给定 Google BigQuery 中的一个表：

User  Timestamp 
A     TIMESTAMP(12/05/2015 12:05:01.8023)
B     TIMESTAMP(9/29/2015 12:15:01.0323)
B     TIMESTAMP(9/29/2015 13:05:01.0233)
A     TIMESTAMP(9/29/2015 14:05:01.0432)
C     TIMESTAMP(8/15/2015 5:05:01.0000)
B     TIMESTAMP(9/29/2015 14:06:01.0233)
A     TIMESTAMP(9/29/2015 14:06:01.0432)

有没有简单的计算方法：

User  Maximum_Number_of_Events_this_User_Had_in_One_Hour  
A     2
B     3
C     1

一小时的时间窗口在哪里是一个参数？

我尝试自己使用 LAG 和分区函数的组合来解决这两个问题：

BigQuery SQL for 28-day sliding window aggregate (without writing 28 lines of SQL)

Bigquery SQL for sliding window aggregate

但是发现这些帖子太不相似了，因为我不是在查找每个时间窗口的人数，而是在一个时间窗口内查找每个人的最大事件数。

Answer 1

这是一种利用时间戳的有序结构的高效简洁方法。

SELECT
  user,
  MAX(per_hour) AS max_event_per_hour
FROM
(
  SELECT 
    user,
    COUNT(*) OVER (PARTITION BY user ORDER BY timestamp RANGE BETWEEN 60 * 60 * 1000000 PRECEDING AND CURRENT ROW) as per_hour,
    timestamp
  FROM 
    [dataset_example_in_question_user_timestamps]
)
GROUP BY user

Answer 2

试试下面的 GBQ。没有测试太多，但对我来说看起来可行

SELECT
  User, Max(events) as Max_Events
FROM (
  SELECT 
    b.User as User, 
    b.Timestamp as Timestamp,
    COUNT(1) as Events
  FROM [your_dataset.your_table] as b
  JOIN (
    SELECT User, Timestamp 
    FROM [your_dataset.your_table]
    ) as w 
  ON w.User = b.User
  WHERE ROUND((TIMESTAMP_TO_SEC(TIMESTAMP(w.Timestamp)) - 
               TIMESTAMP_TO_SEC(TIMESTAMP(b.Timestamp))) / 3600, 1) BETWEEN 0 AND 1
  GROUP BY 1, 2
)
GROUP BY 1

Answer 3

我认为您可以使用这样的查询（在 T-SQL 中）：

SELECT "User", SUM(s) As Maximum_Number_of_Events_this_User_Had_in_One_Hour  
FROM (
    SELECT "User", 1 s
    FROM yourTable
    GROUP BY "User", CAST("Timestamp" As date), DATEPART(Hour, "Timestamp")) As t
GROUP BY "User"