如何使用TSQL识别记录中的记录模式序列？

Question

这对我来说是一个相当新的练习,但我需要找到一种方法来识别表格中的模式序列.例如,假设我有一个类似于以下内容的简单表:

现在我想做的是识别和分组所有具有值为5,9和6的序列模式的记录,并在查询中显示它们.你会如何使用T-SQL完成这项任务？

结果应如下所示:

我已经找到了一些可能实现这一目标的潜在例子,却找不到真正有用的东西.

Answer 1

您可以使用包含在a CTE中的以下查询,以便将序列号分配给序列中包含的值:

;WITH Seq AS (
    SELECT v, ROW_NUMBER() OVER(ORDER BY k) AS rn
    FROM (VALUES(1, 5), (2, 9), (3, 6)) x(k,v)
)

输出:

v   rn
-------
5   1
9   2
6   3

使用上面的方法,CTE您可以识别孤岛,即包含整个序列的连续行的切片:

;WITH Seq AS (
    SELECT v, ROW_NUMBER() OVER(ORDER BY k) AS rn
    FROM (VALUES(1, 5), (2, 9), (3, 6)) x(k,v)
), Grp AS (
SELECT [Key], [Value], 
       ROW_NUMBER() OVER (ORDER BY [Key]) - rn AS grp            
FROM mytable AS m
LEFT JOIN Seq AS s ON m.Value = s.v
)
SELECT *
FROM Grp

输出:

    Key Value   grp
   -----------------
    1   5       0
    2   9       0
    3   6       0
    6   5       3
    7   9       3
    8   6       3

grp 字段可以帮助您准确识别这些岛屿.

您现在需要做的就是过滤掉部分组:

;WITH Seq AS (
    SELECT v, ROW_NUMBER() OVER(ORDER BY k) AS rn
    FROM (VALUES(1, 5), (2, 9), (3, 6)) x(k,v)
), Grp AS (
SELECT [Key], [Value], 
       ROW_NUMBER() OVER (ORDER BY [Key]) - rn AS grp            
FROM mytable AS m
LEFT JOIN Seq AS s ON m.Value = s.v
)
SELECT g1.[Key], g1.[Value]
FROM Grp AS g1
INNER JOIN (
   SELECT grp
   FROM Grp
   GROUP BY grp
   HAVING COUNT(*) = 3 ) AS g2
ON g1.grp = g2.grp

在这里演示

注意:这个答案的最初版本使用INNER JOIN到Seq.如果表包含类似的值5, 42, 9, 6,这将无效,并且42将被INNER JOIN错误地识别为有效的序列过滤掉.感谢@HABO进行此编辑.