SQL：对连续记录进行分组

Question

一个有点棘手的 SQL 问题（我们运行的是 SQL Server 2000）。

我有下表 StoreCount -

WeekEndDate    StoreCount
2010-07-25     359
2010-07-18     359
2010-07-11     358
2010-07-04     358
2010-06-27     358
2010-06-20     358
2010-06-13     358
2010-06-06     359
2010-05-30     360
2010-05-23     360
2010-05-16     360

我想将其转换为以下输出 -

StartDate    EndDate       StoreCount
2010-07-18   2010-07-25    359
2010-06-13   2010-07-11    358
2010-06-06   2010-06-06    359
2010-05-16   2010-05-30    360

正如您所看到的，我想要对商店计数进行分组，仅当它们按顺序一起运行时。

Answer 1

这里有一个挑战，只是它可能有 SS2k 中不可用的语法。它实际上是在 Oracle 上编写的，因为我不再有那个版本的 SS。唯一的问题可能是选择的选择...（自从我使用 SS2k 以来已经有一段时间了，所以很难记住当时哪些功能不可用。）

select min(weekenddate) as start_date, end_date, storecount
from (
select s1.weekenddate
     , (select max(weekenddate)
          from store_stats s2
         where s2.storecount = s1.storecount
           and not exists (select null
                             from store_stats s3
                            where s3.weekenddate < s2.weekenddate
                              and s3.weekenddate > s1.weekenddate
                              and s3.storecount <> s1.storecount)
       ) as end_date
     , s1.storecount
from store_stats s1
) result
group by end_date, storecount
order by 1 desc


START_DATE END_DATE   STORECOUNT
---------- ---------- ----------
2010-07-18 2010-07-25        359
2010-06-13 2010-07-11        358
2010-06-06 2010-06-06        359
2010-05-16 2010-05-30        360

Answer 2

使用光标。我不知道如何在 sql2k 中使用查询来做到这一点。

DECLARE @w datetime
DECLARE @s int
DECLARE @prev_s int
DECLARE @start_w datetime
DECLARE @end_w datetime

CREATE TABLE #zz(start datetime, [end] datetime, StoreCount int)

DECLARE a_cursor CURSOR
FOR SELECT WeekEndDate, StoreCount FROM Line ORDER BY WeekEndDate DESC, StoreCount
OPEN a_cursor
FETCH NEXT FROM a_cursor INTO @w, @s
WHILE @@FETCH_STATUS = 0
BEGIN

    IF @end_w IS NULL 
    BEGIN

        SET @end_w = @w
        SET @start_w = @w     
        SET @prev_s = @s
    END 
    ELSE IF @prev_s <> @s
    BEGIN
       INSERT INTO #zz values(@start_w,  @end_w, @prev_s)

       SET @end_w = @w  
       SET @start_w = @w  
       SET @prev_s = @s 
    END ELSE
        SET @start_w = @w 

    FETCH NEXT FROM a_cursor INTO @w, @s
END
-- add last one
INSERT INTO #zz values(@start_w, @end_w, @prev_s)

CLOSE a_cursor
DEALLOCATE a_cursor

SELECT * FROM #zz ORDER BY 1 DESC
DROP TABLE #zz

Answer 3

好的，这是我的尝试。

DECLARE @curDate DATETIME = (SELECT MIN(WeekEndDate) FROM Table_1);
    DECLARE @curCount INT = (SELECT StoreCount FROM Table_1 WHERE WeekEndDate = @curDate);
    DECLARE @sDate DATETIME = GETDATE()
    DECLARE @eDate DATETIME = 0


    WHILE @eDate < (SELECT MAX(WeekEndDate) FROM Table_1)
    BEGIN
        SELECT @sDate = (SELECT WeekEndDate AS StartDate FROM Table_1 WHERE WeekEndDate = @curDate) -- SELECT START DATE

        -- NOW GET THE END DATE IN THIS GROUP
        DECLARE @d1 DATETIME = @curDate
        DECLARE @d2 DATETIME = @curDate
        DECLARE @loop INT = 1
        WHILE @loop = 1
            BEGIN
                IF ((SELECT StoreCount FROM Table_1 WHERE WeekEndDate = @d1) <> @curCount OR @d1 = (SELECT MAX(WeekEndDate) FROM Table_1)) BEGIN
                    SELECT @eDate = (SELECT TOP(1) WeekEndDate FROM Table_1 WHERE StoreCount = @curCount AND WeekEndDate = @d2 ORDER BY WeekEndDate DESC)
                    SELECT @loop = 0 END
                ELSE BEGIN
                    SELECT @d2 = @d1 
                    SELECT @d1 = (SELECT TOP(1) WeekEndDate FROM Table_1 WHERE WeekEndDate > @d1 ORDER BY WeekEndDate) END
            END


        SELECT @sDate AS StartDate, @eDate AS EndDate, @curCount AS StoreCount   -- DO QHATEVER YOU NEED TO DO WITH THE RECORDS HERE

        SELECT TOP(1) @curDate = WeekEndDate, @curCount = StoreCount
        FROM Table_1
        WHERE WeekEndDate > @eDate
        GROUP BY WeekEndDate, StoreCount
        ORDER BY WeekEndDate ASC

    END

Answer 4

我不确定如何解释这一点，但它似乎为给定的小数据集提供了所需的结果。本质上，它检测序列中值发生变化的点。

我没有看过查询计划，可能会很痛苦。

在Sybase服务器上尝试过，因此语法应该与SQL Server 2K兼容。

SELECT  x.StartDate
        , MIN( y.EndDate ) AS EndDate
        , x.StoreCount
FROM
( SELECT
        wed1.WeekEndDate AS StartDate
        , wed1.StoreCount
FROM
        wed wed1
LEFT JOIN
        wed wed2
ON      wed1.WeekEndDate = DATEADD( DAY, 7, wed2.WeekEndDate )
WHERE
        wed1.StoreCount != ISNULL( wed2.StoreCount, wed1.StoreCount - 1 )
) x,
( SELECT
        wed1.WeekEndDate AS EndDate
FROM
        wed wed1
LEFT JOIN
        wed wed2
ON      wed1.WeekEndDate = DATEADD( DAY, -7, wed2.WeekEndDate )
WHERE
        wed1.StoreCount != ISNULL( wed2.StoreCount, wed1.StoreCount - 1 )
) y
WHERE
        y.EndDate >= x.StartDate
GROUP BY
        x.StartDate
HAVING
        x.StartDate = MIN( x.StartDate )
ORDER BY
        1 DESC

StartDate    EndDate      StoreCount
------------ ------------ -----------
 Jul 18 2010  Jul 25 2010         359
 Jun 13 2010  Jul 11 2010         358
 Jun  6 2010  Jun  6 2010         359
 May 16 2010  May 30 2010         360

Answer 5

尝试这个简单的解决方案：

create table x  (weekEndDate char(10), storeCount int);
insert into x values
('2010-07-25',359),
('2010-07-18',359),
('2010-07-11',358),
('2010-07-04',358),
('2010-06-27',358),
('2010-06-20',358),
('2010-06-13',358),
('2010-06-06',359),
('2010-05-30',360),
('2010-05-23',360),
('2010-05-16',360);
select min(weekenddate) as startdate, max(weekenddate) as enddate, min(storecount) as storecount 
from 
(select weekenddate, storecount, concat(row_number() over (order by weekenddate) -row_number() over (partition by storecount order by weekenddate),'|',storecount) as groupkey from x) w
group by groupkey order by startdate desc;

sqlfiddle