Question

我有以下内容。

Name    Date
A   2011-01-01 01:00:00.000
A   2011-02-01 02:00:00.000
A   2011-03-01 03:00:00.000
B   2011-04-01 04:00:00.000
A   2011-05-01 07:00:00.000

所需的输出是

Name       StartDate                        EndDate
-------------------------------------------------------------------
A          2011-01-01 01:00:00.000         2011-04-01 04:00:00.000    
B          2011-04-01 04:00:00.000         2011-05-01 07:00:00.000    
A          2011-05-01 07:00:00.000         NULL

如何在基于集合的方法中使用TSQL实现相同目的。

DDL与

相同

DECLARE @t TABLE(PersonName VARCHAR(32), [Date] DATETIME) 
INSERT INTO @t VALUES('A', '2011-01-01 01:00:00') 
INSERT INTO @t VALUES('A', '2011-01-02 02:00:00') 
INSERT INTO @t VALUES('A', '2011-01-03 03:00:00') 
INSERT INTO @t VALUES('B', '2011-01-04 04:00:00') 
INSERT INTO @t VALUES('A', '2011-01-05 07:00:00')

Select * from @t

Answer 1

;WITH cte1
     AS (SELECT *,
                ROW_NUMBER() OVER (ORDER BY Date) -
                ROW_NUMBER() OVER (PARTITION BY PersonName
                ORDER BY Date) AS G
         FROM   @t),
     cte2
     AS (SELECT PersonName,
                MIN([Date]) StartDate,
                ROW_NUMBER() OVER (ORDER BY  MIN([Date])) AS rn
         FROM   cte1
         GROUP  BY PersonName,
                   G)
SELECT a.PersonName,
       a.StartDate,
       b.StartDate AS EndDate
FROM   cte2 a
       LEFT JOIN cte2 b
         ON a.rn + 1 = b.rn

因为CTE的结果通常没有实现如果你实现了，你可能会发现你的表现会更好中间结果如下。

DECLARE @t2 TABLE (
  rn         INT IDENTITY(1, 1) PRIMARY KEY,
  PersonName VARCHAR(32),
  StartDate  DATETIME );

INSERT INTO @t2
SELECT PersonName,
       MIN([Date]) StartDate
FROM   (SELECT *,
               ROW_NUMBER() OVER (ORDER BY Date) -
               ROW_NUMBER() OVER (PARTITION BY PersonName
               ORDER BY Date) AS G
        FROM   @t) t
GROUP  BY PersonName,
          G
ORDER  BY StartDate

SELECT a.PersonName,
       a.StartDate,
       b.StartDate AS EndDate
FROM   @t2 a
       LEFT JOIN @t2 b
         ON a.rn + 1 = b.rn

Answer 2

cte的另一个答案是好的。另一种选择是在任何情况下迭代集合。它不是基于设置，但它是另一种方法。

您将需要迭代到A.为每个与其事务对应的记录分配一个唯一的ID，或B.实际获取您的输出。

TSQL不适合迭代记录，特别是如果你有很多，所以我会建议其他一些方法，一个小的.net程序或更好的迭代。

Answer 3

获取行号，以便了解上一条记录的位置。然后，记录下一条记录和下一条记录。当状态改变时，我们有一个候选行。

select 
  state, 
  min(start_timestamp),
  max(end_timestamp)

from
(
    select
        first.state, 
        first.timestamp_ as start_timestamp,
        second.timestamp_ as end_timestamp

        from
        (
            select
                *, row_number() over (order by timestamp_) as id
            from test
        ) as first

        left outer join
        (
            select
                *, row_number() over (order by timestamp_) as id
            from test
        ) as second
        on 
            first.id = second.id - 1 
            and first.state != second.state
) as agg
group by state
    having max(end_timestamp) is not null 

union

-- last row wont have a ending row
--(select state, timestamp_, null from test order by timestamp_ desc limit 1)
    -- I think it something like this for sql server
     (select top state, timestamp_, null from test order by timestamp_ desc)

order by 2
;

使用PostgreSQL进行测试，但也应该与SQL Server一起使用

Answer 4

SELECT
  PersonName,
  StartDate = MIN(Date),
  EndDate
FROM (
  SELECT
    PersonName,
    Date,
    EndDate = (
      /* get the earliest date after current date
         associated with a different person */
      SELECT MIN(t1.Date)
      FROM @t AS t1
      WHERE t1.Date > t.Date
        AND t1.PersonName <> t.PersonName
    )
  FROM @t AS t
) s
GROUP BY PersonName, EndDate
ORDER BY 2

基本上，对于每个Date，我们会在其后找到与其他PersonName相关联的最近日期。这给了我们EndDate，它现在区分了同一个人的连续日期组。

现在我们只需要按PersonName＆amp;分组对数据进行分组。 EndDate并将每个组中的最小Date设为StartDate。是的，当然，按StartDate对数据进行排序。

Answer 5

使用一些差距和群岛理论可以很快地实现这一目标：

WITH CTE as (SELECT PersonName, [Date]
                   , Row_Number() over (ORDER BY [Date])
                     - Row_Number() over (ORDER BY PersonName, [Date]) as Island
             FROM @t)

Select PersonName, Min([Date]), Max([Date])
from CTE
GROUP BY Island, PersonName
ORDER BY Min([Date])

在T-SQL中查找开始和结束日期（基于集）

5 个答案: