NULL时分区

Question

我有一张类似

的表格

Year  Month  ID     Date     Status
--------------------------------------
2013    8   99999   8/1/2013 Status A
2013    9   99999   NULL     NULL
2013    10  99999   NULL     NULL
2013    11  99999   NULL     NULL
2013    12  99999   NULL     NULL
2014    1   99999   NULL     NULL
2014    2   99999   2/5/2014 Status B
2014    3   99999   NULL     NULL
2014    4   99999   NULL     NULL
2014    5   99999   NULL     NULL
2014    6   99999   NULL     NULL
2014    7   99999   NULL     NULL

我想添加一个列，它会给出状态编号，重复到下一次出现状态，然后添加1。

结果：

Year  Month  ID     Date     Status   Value
--------------------------------------------
2013    8   99999   8/1/2013 Status A 1
2013    9   99999   NULL     NULL     1
2013    10  99999   NULL     NULL     1
2013    11  99999   NULL     NULL     1
2013    12  99999   NULL     NULL     1
2014    1   99999   NULL     NULL     1
2014    2   99999   2/5/2014 Status B 2
2014    3   99999   NULL     NULL     2
2014    4   99999   NULL     NULL     2
2014    5   99999   NULL     NULL     2
2014    6   99999   NULL     NULL     2
2014    7   99999   NULL     NULL     2

Nulls是什么让我失望...感谢您的帮助！

编辑：

这是我当前的查询：

DECLARE @DateStart DATETIME
DECLARE @DateEnd DATETIME

SET @DateStart = '8/1/2013'
SET @DateEnd = '7/1/2014'

SELECT    
   P.Year, P.Month, P.ID,
   PP.MaxStatusDate,
   Status
FROM      
    (SELECT    
        *
     FROM      
        (SELECT DISTINCT
            year, Month 
         FROM      
            lu_Calendar
         WHERE     
            Date BETWEEN @DateStart AND @DateEnd) AS A
     CROSS JOIN 
         (SELECT DISTINCT
             ID
          FROM   
             dbo.StatusChangeData) AS B
    ) AS P
LEFT JOIN 
    (SELECT  
        yr, mnth, MaxStatusDate, Status, A.ID
     FROM    
        (SELECT    
            ID, YEAR([ModifiedDate]) AS yr,
            MONTH(ModifiedDate) AS mnth,
            MAX([ModifiedDate]) AS MaxStatusDate
        FROM      
            dbo.StatusChangeData
        GROUP BY  
            ID, YEAR([ModifiedDate]), MONTH(ModifiedDate)) AS A
INNER JOIN 
    dbo.StatusChangeData sce ON sce.ID = A.ID AND A.MaxStatusDate = sce.[ModifiedDate]
) AS PP ON P.Month = pp.mnth AND P.YEAR = PP.yr AND P.ID = PP.ID
WHERE     
    P.ID = 99999

Answer 1

您可以使用相关子查询执行此操作。从本质上讲，这会计算任何给定值之前的非NULL值的数量：

select scd.*,
       (select count(*)
        from StatusChangeData scd2
        where scd2.id = scd.id and
              scd2.status is not null and
              scd2.year*100+scd2.month <= scd.year*100+scd.month
       ) as value
from StatusChangeData scd;