Question

对于此示例，我说我有一个包含两个字段的表AREA varchar(30)和OrderNumber INT。

该表格包含以下数据

AREA      | OrderNumber
Fontana   |       32
Fontana   |       42
Fontana   |       76
Fontana   |       12
Fontana   |        3
Fontana   |       99
RC        |       32
RC        |        1
RC        |        8
RC        |        9
RC        |        4

我想返回

我想要返回的结果是每个区域增加连续值的最长长度。对于Fontana it is 3 (32, 42, 76)。 For RC it is 2 (8,9)

AREA    | LongestLength
Fontana |          3
RC      |          2

我如何在MS Sql 2005上执行此操作？

Answer 1

一种方法是使用跨越每一行的递归CTE。如果行符合条件（增加相同区域的订单号），则将链长增加1。如果没有，你就开始一个新的链：

; with  numbered as
        (
        select  row_number() over (order by area, eventtime) rn
        ,       *
        from    Table1
        )
,       recurse as
        (
        select  rn
        ,       area
        ,       OrderNumber
        ,       1 as ChainLength
        from    numbered
        where   rn = 1
        union all
        select  cur.rn
        ,       cur.area
        ,       cur.OrderNumber
        ,       case
                when cur.area = prev.area 
                     and cur.OrderNumber > prev.OrderNumber 
                     then prev.ChainLength + 1
                else 1
                end
        from    recurse prev
        join    numbered cur
        on      prev.rn + 1 = cur.rn
        )
select  area
,       max(ChainLength)
from    recurse
group by
        area

Live example at SQL Fiddle.

另一种方法是使用查询来查找“中断”，即结束同一区域的递增顺序号序列的行。中断之间的行数是长度。

; with  numbered as
        (
        select  row_number() over (order by area, eventtime) rn
        ,       *
        from    Table1 t1
        )
        -- Select rows that break an increasing chain
,       breaks as
        (
        select  row_number() over (order by cur.rn) rn2
        ,       cur.rn
        ,       cur.Area
        from    numbered cur
        left join
                numbered prev
        on      cur.rn = prev.rn + 1
        where   cur.OrderNumber <= prev.OrderNumber
                or cur.Area <> prev.Area
                or prev.Area is null
        )
        -- Add a final break after the last row
,       breaks2 as
        (
        select  *
        from    breaks
        union all
        select  count(*) + 1
        ,       max(rn) + 1
        ,       null
        from    breaks
        )
select  series_start.area
,       max(series_end.rn - series_start.rn)
from    breaks2 series_start
join    breaks2 series_end
on      series_end.rn2 = series_start.rn2 + 1
group by
        series_start.area

Live example at SQL Fiddle.

Answer 2

您可以通过ROW_NUMBER()进行一些数学计算，找出连续项目的位置。

以下是代码示例：

;WITH rownums AS
(
    SELECT [area], 
        ROW_NUMBER() OVER(PARTITION BY [area] ORDER BY [ordernumber]) AS rid1, 
        ROW_NUMBER() OVER(PARTITION BY [area] ORDER BY [eventtime]) AS rid2
    FROM SomeTable
),
    differences AS 
(
    SELECT [area],
        [calc] = rid1 - rid2
    FROM rownums
),  
    summation AS
(
    SELECT [area], [calc], COUNT(*) AS lengths 
    FROM differences 
    GROUP BY [area], [calc]
)   
SELECT [area], MAX(lengths) AS LongestLength
FROM differences
JOIN summation
    ON differences.[calc] = summation.[calc]
    AND differences.area = calc.area
GROUP BY [area]

因此，如果我按照我的订单编号排序一组行号，而按照我的事件时间排序另一组行号，那么这两个数字之间的差异将始终相同，只要它们的顺序相同即可。

然后，您可以获得按这些差异分组的计数，然后拉出最大的计数以获得所需的数据。

编辑：...... 忽略第一次编辑，我急于求成。

Answer 3

你没有解释为什么RC的最长序列不包括1，而Fontana的确包括32.我认为1被排除，因为它是减少：它来自32.然而，Fontana的32是第一个小组中的项目，我有两个想法如何解释为什么它被认为是增加。这或者正是因为它是该组的第一项，或者因为它也为正（即好像是在0之后，因此增加）。

出于这个答案的目的，我假设后者，即如果一个组的第一个项目是正数则增加。以下脚本实现了以下想法：

按照您几乎忘记提及的AREA列的顺序枚举每个eventtime组中的行。
将枚举集合加入自身，将每一行与其前一行链接起来。
获取行与其前一个值之间差异的符号（将后者默认为0）。此时问题变为gaps-and-islands。
按照＃3中确定的符号对每个AREA组进行分区，并枚举每个子组的行。
找出＃1中的行号与＃4中的行号之间的差异。这将是识别单个条纹的标准（与AREA一起）。

最后，按AREA对结果进行分组，＃3中的符号和＃5的结果对行进行分组，计算行数并获得每AREA的最大数量。

< / LI>

我实现了以上内容：

WITH enumerated AS (
  SELECT
    *,
    row = ROW_NUMBER() OVER (PARTITION BY AREA ORDER BY eventtime)
  FROM atable
),
signed AS (
  SELECT
    this.eventtime,
    this.AREA,
    this.row,
    sgn = SIGN(this.OrderNumber - COALESCE(last.OrderNumber, 0))
  FROM      enumerated AS this
  LEFT JOIN enumerated AS last
    ON this.AREA = last.AREA
   AND this.row  = last.row + 1
),
partitioned AS (
  SELECT
    AREA,
    sgn,
    grp = row - ROW_NUMBER() OVER (PARTITION BY AREA, sgn ORDER BY eventtime)
  FROM signed
)
SELECT DISTINCT
  AREA,
  LongestIncSeq = MAX(COUNT(*)) OVER (PARTITION BY AREA)
FROM partitioned
WHERE sgn = 1
GROUP BY
  AREA,
  grp
;

可以找到一个SQL小提琴演示here。

在SQL中查找连续增加的数字的最长序列

3 个答案: