sql – 按值对行进行分组和计数,直到更改为止

我已经尝试了COUNT-OVER查询,但是仍在为每条消息计算.

SELECT message,COUNT(*) OVER (ORDER BY Timestamp RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

这是我的示例数据：

Timestamp        Message
20150329 00:00   A
20150329 00:01   A
20150329 00:02   B
20150329 00:03   A
20150329 00:04   A
20150329 00:05   A
20150329 00:06   B

我想要关注输出

Message    COUNT
A          2
B          1
A          3
B          1

解决方法

;WITH cte as (
SELECT Messages.Message,Timestamp,ROW_NUMBER() OVER(PARTITION BY Message ORDER BY Timestamp) AS gn,ROW_NUMBER() OVER (ORDER BY Timestamp) AS rn
FROM Messages
),cte2 AS (
SELECT Message,gn,rn,gn - rn  as gb
FROM cte 
),cte3 AS (
SELECT Message,MIN(Timestamp) As Ts,COUNT(1) as Cnt
FROM cte2
GROUP BY Message,gb)
SELECT Message,Cnt FROM cte3
ORDER BY Ts

这是结果集：

Message   Cnt
    A   2
    B   1
    A   3
    B   1

查询可能会更短,但我会以这种方式发布,以便您可以看到正在发生的事情.
结果完全按照要求.这是最重要的部分,我们的想法是对每个分区中的行进行编号,同时对整个集合中的行进行编号,然后如果从另一个中减去一个,则会得到每个分区的“等级”.组.

;WITH cte as (
SELECT Messages.Message,gn - rn  as gb
FROM cte 
)
SELECT * FROM cte2

Message Timestamp           gn  rn  gb
A   2015-03-29 00:00:00.000 1   1   0
A   2015-03-29 00:01:00.000 2   2   0
B   2015-03-29 00:02:00.000 1   3   -2
A   2015-03-29 00:03:00.000 3   4   -1
A   2015-03-29 00:04:00.000 4   5   -1
A   2015-03-29 00:05:00.000 5   6   -1
B   2015-03-29 00:06:00.000 2   7   -5

（编辑：李大同）

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