SQL Server：N 个月内计算行的总和

Question

我是 SQL Server 的新手，并且有一个关于使用条件语句对计算行求和的问题。

我的数据组织如下：

ID  S_DATE     END_DATE   MNum  CHG  DateCHG
---------------------------------------------
1   1/26/2001   2/26/2001   7   NULL   1
1   2/27/2001   3/27/2001   8   1      1
1   3/28/2001   1/9/2003    9   1      21
1   1/10/2003   3/2/2004    11  2      14
1   3/3/2004    10/14/2004  10  -1     7
1   10/15/2004  6/22/2005   9   -1     8
1   6/23/2005   3/9/2008    8   -1    33
1   3/10/2008   1899-12-30  0   NULL    -1299
2   9/23/1993   9/11/2000   3   NULL    84
2   1/1/1999    12/31/1998  3   0   -1
2   9/12/2000   11/13/2001  2   -1  14
2   11/14/2001  1899-12-30  0   NULL    -1223

DateCHG 等于 S_DATE 和 End_Date 之间的月数。我想找到在前一个日期的 3 个月内出现 CHG 的每个 ID 的 CHG 总和。

这是我当前的代码（注意：出于格式化目的，列标题与上面的数据不同。我也无法写入此数据库，因此只能以查询格式写入）

SELECT
     *,  
     CASE 
        WHEN MratingNum = 0 OR
             LAG(MratingNum) OVER (OVER BY MAST_ISSU_NUM, RATG_DATETIME) = 0 OR 
             MAST_ISSU_NUM <> LAG(MAST_ISSU_NUM) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME) --OR
            --LAG(MratingNum) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME) < 12 OR  --By Credit Rating
            --LAG(MratingNum) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME) < 18
           THEN NULL 
           ELSE CAST(MratingNum AS INT) - LAG(MratingNum) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME)
    END AS CHG,
    DATEDIFF(month, RATG_DATETIME, RATG_END_DATETIME) AS DateCHG 
FROM
    MOODYS_DRD.dbo.DEBT_RATG AS t1
LEFT JOIN
    sandbox.dbo.RatingMap AS t2 ON t1.RATG_TXT = t2.MratingValue
WHERE 
    RATG_TYP_CD = 'LT'
ORDER BY 
    MAST_ISSU_NUM, RATG_DATETIME

例如，输出将如下所示：

ID S_DATE   .... SumCHG
1  1/26/2001....   NULL
1  2/27/2001....   NULL
1  3/28/2001....   2
1  1/10/2003....   NULL
1  3/3/2004 ....   NULL

我假设最好的方法是计算 DateCHG 小于 3 的滚动总和，然后对 CHG 列求和？谢谢大家！

编辑：这相当复杂，所以让我尝试另一种提问方式。对于每条记录，我想在 S_DATE 的 3 个月内回顾并找到 CHG 的总和。对于 2001 年 3 月 28 日，这将包括 2/01 和 1/01。 MNum 从 7 变为 9，因此 CHG 的 SUM 为 2。但是从 3/04 开始，过去 3 个月没有变化，因此返回 NULL。我显然想按 ID 执行此操作，因此不想将 ID 2 到 1 的 3 个月重叠。希望现在这更有意义吗？

Answer 1

t0 和t 用于设置数据。

with    t0
          as ( select   *
               from     ( values ( 1, '1/26/2001', '2/26/2001', 7, null, 1),
                        ( 1, '2/27/2001', '3/27/2001', 8, 1, 1),
                        ( 1, '3/28/2001', '1/9/2003', 9, 1, 21),
                        ( 1, '1/10/2003', '3/2/2004', 11, 2, 14),
                        ( 1, '3/3/2004', '10/14/2004', 10, -1, 7),
                        ( 1, '10/15/2004', '6/22/2005', 9, -1, 8),
                        ( 1, '6/23/2005', '3/9/2008', 8, -1, 33),
                        ( 1, '3/10/2008', '1899-12-30', 0, null, -1299),
                        ( 2, '9/23/1993', '9/11/2000', 3, null, 84),
                        ( 2, '1/1/1999', '12/31/1998', 3, 0, -1),
                        ( 2, '9/12/2000', '11/13/2001', 2, -1, 14),
                        ( 2, '11/14/2001', '1899-12-30', 0, null, -1223) ) t ( ID, S_DATE, END_DATE, MNum, CHG, DateCHG )
             ),
        t as ( select   t0.ID ,
                        cast(t0.S_DATE as date) S_DATE ,
                        cast(t0.END_DATE as date) END_DATE ,
                        t0.MNum ,
                        t0.CHG ,
                        t0.DateCHG
               from     t0
             )
    select  case when Cnt >= 3 then p.CHG
            end SumCHG,
            *
    from    t
            outer apply ( select    sum(u.CHG) CHG ,
                                    count(*) Cnt
                          from      t u
                          where     u.ID = t.ID
                                    and u.S_DATE between dateadd(month, -3,
                                                              t.S_DATE)
                                                 and     t.S_DATE
                        ) p
    order by t.ID ,
        t.S_DATE;

为您的表格使用 CTE，

;with t as (
SELECT
     *,  
     CASE 
        WHEN MratingNum = 0 OR
             LAG(MratingNum) OVER (OVER BY MAST_ISSU_NUM, RATG_DATETIME) = 0 OR 
             MAST_ISSU_NUM <> LAG(MAST_ISSU_NUM) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME) --OR
            --LAG(MratingNum) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME) < 12 OR  --By Credit Rating
            --LAG(MratingNum) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME) < 18
           THEN NULL 
           ELSE CAST(MratingNum AS INT) - LAG(MratingNum) OVER (ORDER BY MAST_ISSU_NUM, RATG_DATETIME)
    END AS CHG,
    DATEDIFF(month, RATG_DATETIME, RATG_END_DATETIME) AS DateCHG 
FROM
    MOODYS_DRD.dbo.DEBT_RATG AS t1
LEFT JOIN
    sandbox.dbo.RatingMap AS t2 ON t1.RATG_TXT = t2.MratingValue
WHERE 
    RATG_TYP_CD = 'LT'
)
    select  case when Cnt >= 3 then p.CHG
            end SumCHG,
            *
    from    t
            outer apply ( select    sum(u.CHG) CHG ,
                                    count(*) Cnt
                          from      t u
                          where     u.ID = t.ID
                                    and u.S_DATE between dateadd(month, -3,
                                                              t.S_DATE)
                                                 and     t.S_DATE
                        ) p
    order by t.ID ,
        t.S_DATE;