如何抓取“下一个"偏移量可变时发生事件?

问题描述

我在Oracle数据库中有一个交易表.我正在尝试为涉及多种交易类型的交付系统收集一份报告.实际上，请求"类型可以是四个子类型之一(在此示例中为"A"，"B"，"C"和"D")，而传递"类型可以是四个不同子类型之一类型("PULL"，"PICKUP"，"MAIL").从请求"到交货"之间可以有1到5笔交易，而且交付"类型中的许多也是中间交易.例如:

I have a table of transactions in an Oracle database. I am attempting to pull a report together for a delivery system involving a number of transaction types. The "request" type can actually be one of four sub-types ('A', 'B', 'C', and 'D' for this example), and the "delivery" type can be one of four different sub-types ('PULL', 'PICKUP', 'MAIL'). There can be anywhere from 1 to 5 transactions to get an item from "request" to "delivery, and a number of the "delivery" types are also intermediary transactions. Example:

Item | Transaction | Timestamp
001  | REQ-A       | 2014-07-31T09:51:32Z
002  | REQ-B       | 2014-07-31T09:55:53Z
003  | REQ-C       | 2014-07-31T10:01:15Z
004  | REQ-D       | 2014-07-31T10:02:29Z
005  | REQ-A       | 2014-07-31T10:05:47Z
002  | PULL        | 2014-07-31T10:20:04Z
002  | MAIL        | 2014-07-31T10:20:06Z
001  | PULL        | 2014-07-31T10:22:21Z
001  | TRANSFER    | 2014-07-31T10:22:23Z
003  | PULL        | 2014-07-31T10:24:10Z
003  | TRANSFER    | 2014-07-31T10:24:12Z
004  | PULL        | 2014-07-31T10:26:28Z
005  | PULL        | 2014-07-31T10:28:42Z
005  | TRANSFER    | 2014-07-31T10:28:44Z
001  | ARRIVE      | 2014-07-31T11:45:01Z
001  | PICKUP      | 2014-07-31T11:45:02Z
003  | ARRIVE      | 2014-07-31T11:47:44Z
003  | PICKUP      | 2014-07-31T11:47:45Z
005  | ARRIVE      | 2014-07-31T11:49:45Z
005  | PICKUP      | 2014-07-31T11:49:46Z

我需要的是这样的报告:

What I need is a report like:

Item | Start Tx | End Tx | Time
001  | REQ-A    | PICKUP | 1:53:30
002  | REQ-B    | MAIL   | 0:24:13
003  | REQ-C    | PICKUP | 1:46:30
004  | REQ-D    | PULL   | 0:23:59
005  | REQ-A    | PICKUP | 1:43:59

我所拥有的:

Item | Start Tx | End Tx   | Time
001  | REQ-A    | PULL     | 0:30:49
001  | REQ-A    | TRANSFER | 0:30:51
001  | REQ-A    | ARRIVE   | 1:53:29
001  | REQ-A    | PICKUP   | 1:53:30
002  | REQ-B    | PULL     | 0:24:11
002  | REQ-B    | MAIL     | 0:24:13
003  | REQ-C    | PULL     | 0:22:55
003  | REQ-C    | TRANSFER | 0:22:57
003  | REQ-C    | ARRIVE   | 1:46:29
003  | REQ-C    | PICKUP   | 1:46:30
004  | REQ-D    | PULL     | 0:23:59
005  | REQ-A    | PULL     | 0:22:55
005  | REQ-A    | TRANSFER | 0:22:57
005  | REQ-A    | ARRIVE   | 1:43:58
005  | REQ-A    | PICKUP   | 1:43:59

我正在做什么以获取数据:

What I'm doing to get that data:

SELECT Item, Transaction, nextTransaction, nextTimestamp - Timestamp
FROM (
    SELECT Item, Transaction, Timestamp,
      LEAD(Transaction, 5) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTransaction"
      LEAD(Timestamp, 5) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTimestamp"
    FROM Transactions
    UNION ALL
    SELECT Item, Transaction, Timestamp,
      LEAD(Transaction, 4) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTransaction"
      LEAD(Timestamp, 4) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTimestamp"
    FROM Transactions
    UNION ALL
    SELECT Item, Transaction, Timestamp,
      LEAD(Transaction, 3) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTransaction"
      LEAD(Timestamp, 3) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTimestamp"
    FROM Transactions
    UNION ALL
    SELECT Item, Transaction, Timestamp,
      LEAD(Transaction, 2) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTransaction"
      LEAD(Timestamp, 2) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTimestamp"
    FROM Transactions
    UNION ALL
    SELECT Item, Transaction, Timestamp,
      LEAD(Transaction, 1) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTransaction"
      LEAD(Timestamp, 1) OVER (PARTITION BY Item ORDER BY Timestamp) AS "nextTimestamp"
    FROM Transactions
)
WHERE nextTransaction IS NOT NULL
AND Transaction IN ('REQ-A', 'REQ-B', 'REQ-C', 'REQ-D')

我可以在脚本中手动解析它(也许这实际上是最好的做法)，但是为了学习起见，我想知道是否有可能单独使用SQL确实可以做到这一点.

I could manually parse this in a script (and perhaps that's actually the best course of action), but for the sake of learning, I'd like to know if it's possible to actually do this with SQL alone.

推荐答案

听起来您想要基于时间的第一个和最后一个事务.我认为以下是您想要的:

It sounds like you want the first and last transactions based on time. I think the following does what you want:

select item,
       min(transaction) keep (dense_rank first order by timestamp) as StartTx,
       min(transaction) keep (dense_rank last order by timestamp) as EndTx,
       max(timestamp) - min(timestamp)
from transactions t
group by item;

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