Google BigQuery：滚动计数不同

Question

我有一张表，其中只是日期和用户 ID 的列表（未汇总）。

我们通过计算过去 45 天内出现的不同 ID 数量，为给定日期定义了一个名为活跃用户的指标。

我正在尝试在 BigQuery 中运行一个查询，该查询每天返回当天加上当天的活跃用户数（统计从 45 天前到今天的不同用户）。

我尝试过窗口函数，但不知道如何根据列中的日期值定义范围。相反，我相信下面的查询可以在 MySQL 这样的数据库中运行，但在 BigQuery 中则不行。

SELECT 
  day,
  (SELECT 
    COUNT(DISTINCT visid) 
   FROM daily_users
   WHERE day BETWEEN DATE_ADD(t.day, -45, "DAY") AND t.day
   ) AS active_users
FROM daily_users AS t
GROUP BY 1

这在 BigQuery 中不起作用：“SELECT 子句中不允许子选择。”

如何在 BigQuery 中执行此操作？

Answer 1

BigQuery documentation 声称 count(distinct) 用作窗口函数。但是，这对您没有帮助，因为您不是在寻找传统的窗框。

一种方法是在访问后为每个日期添加一条记录：

select theday, count(distinct visid)
from (select date_add(u.day, n.n, "day") as theday, u.visid
      from daily_users u cross join
           (select 1 as n union all select 2 union all . . .
            select 45
           ) n
     ) u
group by theday;

注意：在 BigQuery 中生成一系列 45 个整数可能有更简单的方法。

Answer 2

以下内容应该适用于 BigQuery

#legacySQL
SELECT day, active_users FROM (
  SELECT 
    day, 
    COUNT(DISTINCT id) 
      OVER (ORDER BY ts RANGE BETWEEN 45*24*3600 PRECEDING AND CURRENT ROW) AS active_users
  FROM (
    SELECT day, id, TIMESTAMP_TO_SEC(TIMESTAMP(day)) AS ts 
    FROM daily_users
  )
) GROUP BY 1, 2 ORDER BY 1  

以上假设day 字段表示为“2016-01-10”格式。
如果不是这种情况，您应该在最内部选择中调整TIMESTAMP_TO_SEC(TIMESTAMP(day))

另外请查看 BigQuery 中的 COUNT(DISTINC) 详细信息

BigQuery 标准 SQL 更新

#standardSQL
SELECT 
  day, 
  (SELECT COUNT(DISTINCT id) FROM UNNEST(active_users) id) AS active_users
FROM (
  SELECT 
    day, 
    ARRAY_AGG(id) 
      OVER (ORDER BY ts RANGE BETWEEN 3888000 PRECEDING AND CURRENT ROW) AS active_users
  FROM (
    SELECT day, id,  UNIX_DATE(PARSE_DATE('%Y-%m-%d', day)) * 24 * 3600 AS ts 
    FROM daily_users
  )
) 
GROUP BY 1, 2 
ORDER BY 1  

您可以使用下面的虚拟样本测试/玩它

#standardSQL
WITH daily_users AS (
  SELECT 1 AS id, '2016-01-10' AS day UNION ALL
  SELECT 2 AS id, '2016-01-10' AS day UNION ALL
  SELECT 1 AS id, '2016-01-11' AS day UNION ALL
  SELECT 3 AS id, '2016-01-11' AS day UNION ALL
  SELECT 1 AS id, '2016-01-12' AS day UNION ALL
  SELECT 1 AS id, '2016-01-12' AS day UNION ALL
  SELECT 1 AS id, '2016-01-12' AS day UNION ALL
  SELECT 1 AS id, '2016-01-13' AS day
)
SELECT 
  day, 
  (SELECT COUNT(DISTINCT id) FROM UNNEST(active_users) id) AS active_users
FROM (
  SELECT 
    day, 
    ARRAY_AGG(id) 
      OVER (ORDER BY ts RANGE BETWEEN 86400 PRECEDING AND CURRENT ROW) AS active_users
  FROM (
    SELECT day, id,  UNIX_DATE(PARSE_DATE('%Y-%m-%d', day)) * 24 * 3600 AS ts 
    FROM daily_users
  )
) 
GROUP BY 1, 2 
ORDER BY 1