Question

我有一个大数据集，为了这个问题的目的有3个字段：

组标识符
从日期
至今

在任何给定的行上，From Date将始终小于To Date但在每个组中，由日期对表示的时间段（没有特定顺序）可以重叠，包含一个在另一个，甚至是相同的。

我最终想要的是一个查询，它将每个组的结果压缩到连续的时间段。例如，一个看起来像这样的组：

| Group ID | From Date  | To Date    |
--------------------------------------
| A        | 01/01/2012 | 12/31/2012 |
| A        | 12/01/2013 | 11/30/2014 |
| A        | 01/01/2015 | 12/31/2015 |
| A        | 01/01/2015 | 12/31/2015 |
| A        | 02/01/2015 | 03/31/2015 |
| A        | 01/01/2013 | 12/31/2013 |

会导致：

| Group ID | From Date  | To Date    |
--------------------------------------
| A        | 01/01/2012 | 11/30/2014 |
| A        | 01/01/2015 | 12/31/2015 |

我已经阅读了很多关于日期包装的文章，但我无法弄清楚如何将其应用到我的数据集中。

如何构建一个能够给我这些结果的查询？

Answer 1

“Microsoft®SQLServer®2012使用窗口函数的高性能T-SQL”一书中提供的解决方案

;with C1 as(
select GroupID, FromDate as ts, +1 as type, 1 as sub
  from dbo.table_name
union all
select GroupID, dateadd(day, +1, ToDate) as ts, -1 as type, 0 as sub
  from dbo.table_name),
C2 as(
select C1.*
     , sum(type) over(partition by GroupID order by ts, type desc
                      rows between unbounded preceding and current row) - sub as cnt
  from C1),
C3 as(
select GroupID, ts, floor((row_number() over(partition by GroupID order by ts) - 1) / 2 + 1) as grpnum
  from C2
  where cnt = 0)

select GroupID, min(ts) as FromDate, dateadd(day, -1, max(ts)) as ToDate
  from C3
  group by GroupID, grpnum;

创建表格：

if object_id('table_name') is not null
  drop table table_name
create table table_name(GroupID varchar(100), FromDate datetime,ToDate datetime)
insert into table_name
select 'A', '01/01/2012', '12/31/2012' union all
select 'A', '12/01/2013', '11/30/2014' union all
select 'A', '01/01/2015', '12/31/2015' union all
select 'A', '01/01/2015', '12/31/2015' union all
select 'A', '02/01/2015', '03/31/2015' union all
select 'A', '01/01/2013', '12/31/2013'

Answer 2

; with 
cte as
(
    select  *, rn = row_number() over (partition by [Group ID] order by [From Date])
    from    tbl
),
rcte as
(
    select  rn, [Group ID], [From Date], [To Date], GrpNo = 1, GrpFrom = [From Date], GrpTo = [To Date]
    from    cte
    where   rn  = 1

    union all

    select  c.rn, c.[Group ID], c.[From Date], c.[To Date], 
        GrpNo = case    when    c.[From Date] between r.GrpFrom and dateadd(day, 1, r.GrpTo)
                or  c.[To Date]   between r.GrpFrom and r.GrpTo
                then    r.GrpNo
                else    r.GrpNo + 1
                end,
        GrpFrom= case   when    c.[From Date] between r.GrpFrom and dateadd(day, 1, r.GrpTo)
                or  c.[To Date]   between r.GrpFrom and r.GrpTo
                then    case when c.[From Date] > r.GrpFrom then c.[From Date] else r.GrpFrom end
                else    c.[From Date] 
                end,
        GrpTo  = case   when    c.[From Date] between r.GrpFrom and dateadd(day, 1, r.GrpTo)
                or  c.[To Date]   between r.GrpFrom and dateadd(day, 1, r.GrpTo)
                then    case when c.[To Date] > r.GrpTo then c.[To Date] else r.GrpTo end
                else    c.[To Date]  
                end

    from    rcte r
        inner join cte c    on  r.[Group ID]    = c.[Group ID]
                    and r.rn        = c.rn - 1
)
select  [Group ID], min(GrpFrom), max(GrpTo)
from    rcte
group by [Group ID], GrpNo

Answer 3

我使用Calendar表。这张表只列出了几十年的日期列表。

CREATE TABLE [dbo].[Calendar](
    [dt] [date] NOT NULL,
CONSTRAINT [PK_Calendar] PRIMARY KEY CLUSTERED 
(
    [dt] ASC
))

populate such table的方法有很多种。

例如，从1900-01-01开始的100K行（~270年）：

INSERT INTO dbo.Calendar (dt)
SELECT TOP (100000) 
    DATEADD(day, ROW_NUMBER() OVER (ORDER BY s1.[object_id])-1, '19000101') AS dt
FROM sys.all_objects AS s1 CROSS JOIN sys.all_objects AS s2
OPTION (MAXDOP 1);

获得Calendar表后，以下是如何使用它。

每个原始行都与Calendar表连接，以返回与From和To之间的日期一样多的行。

然后删除可能的重复项。

然后通过在两个序列中对行进行编号来获得经典的间隙和岛屿。

然后将找到的岛屿分组在一起以获得新的From和To。

示例数据

我添加了第二组。

DECLARE @T TABLE (GroupID int, FromDate date, ToDate date);
INSERT INTO @T (GroupID, FromDate, ToDate) VALUES
(1, '2012-01-01', '2012-12-31'),
(1, '2013-12-01', '2014-11-30'),
(1, '2015-01-01', '2015-12-31'),
(1, '2015-01-01', '2015-12-31'),
(1, '2015-02-01', '2015-03-31'),
(1, '2013-01-01', '2013-12-31'),
(2, '2012-01-01', '2012-12-31'),
(2, '2013-01-01', '2013-12-31');

<强>查询

WITH
CTE_AllDates
AS
(
    SELECT DISTINCT
        T.GroupID
        ,CA.dt
    FROM
        @T AS T
        CROSS APPLY
        (
            SELECT dbo.Calendar.dt
            FROM dbo.Calendar
            WHERE
                dbo.Calendar.dt >= T.FromDate
                AND dbo.Calendar.dt <= T.ToDate
        ) AS CA
)
,CTE_Sequences
AS
(
    SELECT
        GroupID
        ,dt
        ,ROW_NUMBER() OVER(PARTITION BY GroupID ORDER BY dt) AS Seq1
        ,DATEDIFF(day, '2001-01-01', dt) AS Seq2
        ,DATEDIFF(day, '2001-01-01', dt) - 
            ROW_NUMBER() OVER(PARTITION BY GroupID ORDER BY dt) AS IslandNumber
    FROM CTE_AllDates
)
SELECT
    GroupID
    ,MIN(dt) AS NewFromDate
    ,MAX(dt) AS NewToDate
FROM CTE_Sequences
GROUP BY GroupID, IslandNumber
ORDER BY GroupID, NewFromDate;

<强>结果

+---------+-------------+------------+
| GroupID | NewFromDate | NewToDate  |
+---------+-------------+------------+
|       1 | 2012-01-01  | 2014-11-30 |
|       1 | 2015-01-01  | 2015-12-31 |
|       2 | 2012-01-01  | 2013-12-31 |
+---------+-------------+------------+

Answer 4

一种几何方法

在这里和elsewhere，我注意到该日期打包问题没有提供解决此问题的几何方法。毕竟，任何范围（包括日期范围）都可以解释为一行。那么为什么不将它们转换为sql几何类型并利用 geometry::UnionAggregate合并范围。所以我刺了一下在您的帖子中看到它。

代码说明

在“数字”中：

我建立了一个表示序列的表
以您最喜欢的方式将其替换成数字表。
对于联合操作，您将永远不需要更多的行您原始的表格，所以我只是以它为基础来构建它。

在“ mergeLines”中：

我将日期转换为浮点数并使用这些浮点数创建几何点。
在这个问题上，我们正在 “整数空间”，这意味着没有时间因素，因此与结束日期相隔一天的某个范围内的开始日期在另一个应该与另一个合并。为了要做合并发生后，我们需要转换为“真实空间”，因此我们在所有范围的末尾加1（我们稍后会撤消）。
然后我通过STUnion和STEnvelope连接这些点。
最后，我通过UnionAggregate合并所有这些行。所结果的 “线”几何对象可能包含多条线，但是如果它们重叠，它们变成一行。

在外部查询中：

我使用数字CTE提取“行”中的各个行。
我将这些行包裹起来，以确保在此处存储行仅作为其两个端点。
我读取了端点x值并将其转换回其时间表示形式，确保将它们放回“整数空间”。

代码

with

    numbers as (

        select  row_number() over (order by (select null)) i 
        from    @spans -- Where I put your data

    ),

    mergeLines as (

        select      groupId,
                    lines = geometry::UnionAggregate(line)
        from        @spans
        cross apply (select 
                        startP = geometry::Point(convert(float,fromDate), 0, 0),
                        stopP = geometry::Point(convert(float,toDate) + 1, 0, 0)
                    ) pointify
        cross apply (select line = startP.STUnion(stopP).STEnvelope()) lineify
        group by    groupId 

    )

    select      groupId, fromDate, toDate 
    from        mergeLines ml
    join        numbers n on n.i between 1 and ml.lines.STNumGeometries()
    cross apply (select line = ml.lines.STGeometryN(i).STEnvelope()) l
    cross apply (select 
                    fromDate = convert(datetime, l.line.STPointN(1).STX),
                    toDate = convert(datetime, l.line.STPointN(3).STX) - 1
                ) unprepare
    order by    groupId, fromDate;

使用SQL缩短时间段

4 个答案:

一种几何方法

代码说明

代码