标记记录孤岛

Question

我有这个数据集：

Id	PrevId	NextId	Product	Process	Date
1	NULL	4	Product 1	Process A	2021-04-24
2	NULL	3	Product 2	Process A	2021-04-24
3	2	5	Product 2	Process A	2021-04-24
4	1	7	Product 1	Process B	2021-04-26
5	3	6	Product 2	Process B	2021-04-24
6	5	NULL	Product 2	Process B	2021-04-24
7	4	9	Product 1	Process B	2021-04-29
9	7	10	Product 1	Process A	2021-05-01
10	9	15	Product 1	Process A	2021-05-03
15	10	19	Product 1	Process A	2021-05-04
19	15	NULL	Product 1	Process C	2021-05-05

对于每个产品，我需要标记 consecutive/islands 具有相同 Process 的记录，例如：

Id	PrevId	NextId	Product	Process	Date	Tag
1	NULL	4	Product 1	Process A	2021-04-24	1
4	1	7	Product 1	Process B	2021-04-26	2
7	4	9	Product 1	Process B	2021-04-29	2
9	7	10	Product 1	Process A	2021-05-01	3
10	9	15	Product 1	Process A	2021-05-03	3
15	10	19	Product 1	Process A	2021-05-04	3
19	15	NULL	Product 1	Process C	2021-05-05	4

一个产品要经过多个过程-es，并且可以多次经过同一个过程。

我基本上需要生成Tag列，其背后的逻辑是具有相同Process的连续记录应该组合在一起但是需要注意的是，相同的过程可能会出现在更远的地方，但应该被视为一个新的组。

我已经尝试了基本的窗口函数（ROW_NUMBER 和 DENSE_RANK），但问题是那些计算在分区内而不是跨个分区。

Answer 1

您可以使用 lag() 来确定值相同的地方。然后累加：

select t.*,
       1 + sum(case when process = prev_process then 0 else 1 end) over (partition by producct order by id) as tag
from (select t.*,
             lag(process) over (partition by product order by id) as prev_process
      from t
     ) t;

Here 是一个 db<>fiddle.

Answer 2

如果您不必验证 prevId 和 nextId（也就是说，如果您的数据已经正确排序），您可以尝试以下操作：

WITH cte AS(
SELECT *
       , ROW_NUMBER() OVER (PARTITION BY Product ORDER BY [Date]) x
       , DENSE_RANK() OVER (PARTITION BY Product, Process ORDER BY [Date]) y
  FROM T1
  WHERE product = 'Product 1'
),
cteTag AS(
SELECT Id, PrevId, NextId, Product, Process, [Date], x-y AS Tag_
  FROM cte
)
SELECT Id, PrevId, NextId, Product, Process, [Date], DENSE_RANK() OVER (PARTITION BY Product ORDER BY Tag_) AS Tag
  FROM cteTag
ORDER BY [Date]

标记记录孤岛

Tag islands of records

sql

sql-server

gaps-and-islands