SQL 计算 window 中出现的次数

Question

我有用户登录日期。我的要求是跟踪过去 90 天内登录的用户数 window。

我对 SQL 和 Teradata 都不熟悉，我无法按需要使用 window 功能。

我需要以下结果，其中 ACTIVE 是前 90 天 window 中出现的唯一 USER_IDs 的计数。

DATES        ACTIVE_IN_WINDOW
12/06/2018     20
13/06/2018     45                 
14/06/2018     65 
15/06/2018     73 
17/06/2018     24      
18/06/2018     87  
19/06/2018     34
20/06/2018     51

目前我的脚本如下

这里就是这一行我搞不对

COUNT ( USER_ID) OVER (PARTITION BY USER_ID ORDER BY EVT_DT ROWS BETWEEN 90 PRECEDING AND  0 FOLLOWING)

我怀疑我需要一组不同的函数来完成这项工作。

SELECT    b.DATES , a.ACTIVE_IN_WINDOW

FROM    

(
        SELECT 

        CAST(CALENDAR_DATE AS DATE) AS DATES FROM SYS_CALENDAR.CALENDAR

        WHERE DATES BETWEEN ADD_MONTHS(CURRENT_DATE, - 10)  AND CURRENT_DATE
) b

LEFT JOIN

(
        SELECT    USER_ID   , EVT_DT 

        , COUNT ( USER_ID) OVER (PARTITION BY USER_ID ORDER BY EVT_DT ROWS BETWEEN 90 PRECEDING AND  0 FOLLOWING) AS ACTIVE_IN_WINDOW

        FROM ENV0.R_ONBOARDING
) a

ON a.EVT_DT = b.DATES

ORDER BY b.DATES

感谢您的帮助。

Answer 1

如果您的数据不是太大，子查询可能是最简单的方法：

SELECT c.dte,
       (SELECT COUNT(DISTINCT o.USER_ID)
        FROM ENV0.R_ONBOARDING o
        WHERE o.EVT_DT > ADD_MONTHS(dte, -3) AND
              o.EVT_DT <= dte
       ) as three_month_count
FROM (SELECT CAST(CALENDAR_DATE AS DATE) AS dte
      FROM SYS_CALENDAR.CALENDAR
      WHERE CALENDAR_DATE BETWEEN ADD_MONTHS(CURRENT_DATE, - 10)  AND CURRENT_DATE
     ) c;

您可能希望从比 3 个月更短的时间范围开始，以查看查询的执行情况。

Answer 2

逻辑类似于 Gordon'，但是 非等值连接 而不是 相关标量子查询 通常更有效在 Teradata 上：

SELECT b.DATES , Count(DISTINCT USER_ID)
FROM
 (
   SELECT CALENDAR_DATE AS DATES 
   FROM SYS_CALENDAR.CALENDAR
   WHERE DATES BETWEEN Add_Months(Current_Date, - 10)  AND Current_Date
 ) b
LEFT JOIN
 ( -- apply DISTINCT before aggregation to reduce intermediate spool
   SELECT DISTINCT USER_ID, EVT_DT
   FROM ENV0.R_ONBOARDING
 ) AS a
ON a.EVT_DT BETWEEN Add_Months(b.DATES,-3) AND b.DATES
GROUP BY 1
ORDER BY 1

当然，这将需要一个大线轴和很多 CPU。

编辑：

切换到周可以减少开销，我使用日期而不是周数（修改其他范围更容易）：

SELECT b.Week , Count(DISTINCT USER_ID) 
FROM
 ( -- Return only Mondays instead of DISTINCT over all days 
   SELECT calendar_date AS Week
   FROM SYS_CALENDAR.CALENDAR 
   WHERE CALENDAR_DATE BETWEEN Add_Months(Current_Date, -9) AND Current_Date
     AND day_of_week = 2 -- 2 = Monday
 ) b 
LEFT JOIN 
 (
   SELECT DISTINCT USER_ID,
     -- td_monday returns the previous Monday, but we need the following monday
     -- covers the previous Tuesday up to the current Monday
            Td_Monday(EVT_DT+6) AS PERIOD_WEEK
   FROM ENV0.R_ONBOARDING
   -- You should add another condition to limit the actually covered date range, e.g.
   -- where EVT_DT BETWEEN Add_Months(b.DATES,-13) AND b.DATES
 ) AS a 
ON a.PERIOD_WEEK BETWEEN b.Week-(12*7) AND b.Week 
GROUP BY 1 
ORDER BY 1

解释应该复制日历作为产品连接的准备，否则您可能需要在 Volatile Table 中具体化日期。最好不要使用 sys_calendar，没有统计数据，例如优化器不知道每个 week/month/year 有多少天，等等。检查你的系统，应该有一个日历 table 为你公司的需要设计（所有列都有统计数据）

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