Loops Teradata的While循环

世界

我正在试图找到一种方法来将多个事件编译在一起。数据如下所示：

基本上，它是一系列带有事件日志的行数据

我希望生成这些行事件的聚合，这样，如果在另一个结束后的30秒内发生新事件，它会将时间合并在一起。但是，如果事件日志没有邻接事件，则不会捕获它。这些事件是“个人”特有的

我设想输出如下所示：

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我的直觉建议使用某种while循环，但我不确定从哪里开始

使用递归CTE可以实现这一点

---

将MYTABLE更改为您的tablename

您可以使用递归CTE实现这一点

---

将MYTABLE更改为您的tablename

不需要递归，也不需要非常难写或在光标上循环

SELECT
   Person,
   Min(starttime),
   Max(starttime),
   -- get a concatenated string
   Trim(Trailing ',' FROM (XmlAgg(Reason || ',' ORDER BY Reason ) (VARCHAR(1000))))
FROM
 (
   SELECT Person, Start_timestamp, Stop_timestamp, Reason,
     -- assign the same number to all rows within 30 seconds 
     Sum(flag) Over
     Over (PARTITION BY Person
           ORDER BY Start_timestamp
           ROWS Unbounded Preceding) AS grp
   FROM
    (
      SELECT Person, Start_timestamp, Stop_timestamp, Reason,
         -- check if previous end is within 30 seconds of the current start
         CASE WHEN Lag(Stop_timestamp) 
                   Over (PARTITION BY Person
                         ORDER BY Start_timestamp) + INTERVAL '30' SECOND < Start_timestamp
              THEN 0
              ELSE 1
         END AS flag
      FROM tab
    ) AS dt
 ) AS dt
-- aggregate per person and group
GROUP BY Person, grp

---

如果您的Teradata版本支持sessione，那么您可以简化组计算，但我无法编写这种特殊语法：-

不需要递归，也很难编写或在游标上循环

SELECT
   Person,
   Min(starttime),
   Max(starttime),
   -- get a concatenated string
   Trim(Trailing ',' FROM (XmlAgg(Reason || ',' ORDER BY Reason ) (VARCHAR(1000))))
FROM
 (
   SELECT Person, Start_timestamp, Stop_timestamp, Reason,
     -- assign the same number to all rows within 30 seconds 
     Sum(flag) Over
     Over (PARTITION BY Person
           ORDER BY Start_timestamp
           ROWS Unbounded Preceding) AS grp
   FROM
    (
      SELECT Person, Start_timestamp, Stop_timestamp, Reason,
         -- check if previous end is within 30 seconds of the current start
         CASE WHEN Lag(Stop_timestamp) 
                   Over (PARTITION BY Person
                         ORDER BY Start_timestamp) + INTERVAL '30' SECOND < Start_timestamp
              THEN 0
              ELSE 1
         END AS flag
      FROM tab
    ) AS dt
 ) AS dt
-- aggregate per person and group
GROUP BY Person, grp

---

如果您的Teradata版本支持Sessione，您可以简化组计算，但我无法编写此syntaxc即席：-

这与我所希望的非常接近。谢谢dnoeth。这和我希望的非常接近。谢谢你，诺思。