当PRECEDING范围为NULL ...多于1列时，TSQL移动AVG返回null

如何解决当PRECEDING范围为NULL ...多于1列时，TSQL移动AVG返回null

您好，我的表格中有几列，并且如果所需的前一行为空，则希望移动平均值返回空。

    CREATE TABLE dbo.TESTMOVINGAVG
(VDATE DATE,V1 SMALLINT,V2 SMALLINT)

INSERT INTO dbo.TESTMOVINGAVG (VDATE,V1,V2) VALUES ('01-01-2020',4,NULL)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-02-2020',3,V2) VALUES ('01-03-2020',1,V2) VALUES ('01-04-2020',9,V2) VALUES ('01-05-2020',12,V2) VALUES ('01-06-2020',4)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-07-2020',8)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-08-2020',15,12)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-09-2020',5,17)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-10-2020',10,9)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-11-2020',14,2)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-12-2020',5)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-13-2020',8,6)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-14-2020',7,29)
INSERT INTO dbo.TESTMOVINGAVG (VDATE,V2) VALUES ('01-15-2020',V2) VALUES ('01-16-2020',2,V2) VALUES ('01-17-2020',10)

SELECT VDATE,CASE WHEN ROW_NUMBER() OVER(ORDER BY VDATE ) > 4 AND V1 IS NOT NULL
       THEN
       AVG(V1) OVER (ORDER BY VDATE ASC ROWS BETWEEN 4 PRECEDING AND CURRENT ROW)
       ELSE NULL 
       END AS V1MOVAVG,CASE WHEN ROW_NUMBER() OVER(ORDER BY VDATE ) > 4 AND V2 IS NOT NULL
       THEN
       AVG(V2) OVER (ORDER BY VDATE ASC ROWS BETWEEN 4 PRECEDING AND CURRENT ROW)
       ELSE NULL 
       END AS V2MOVAVG
FROM TESTMOVINGAVG 

我明白了

    VDATE   V1  V1MOVAVG    V2MOVAVG
2020-01-01  4   NULL    NULL
2020-01-02  3   NULL    NULL
2020-01-03  1   NULL    NULL
2020-01-04  9   NULL    NULL
2020-01-05  12  5   NULL
2020-01-06  3   5   4
2020-01-07  4   5   6
2020-01-08  15  8   8
2020-01-09  5   7   10
2020-01-10  10  7   10
2020-01-11  14  9   9
2020-01-12  12  11  9
2020-01-13  8   9   7
2020-01-14  7   10  10
2020-01-15  4   9   9
2020-01-16  2   6   10
2020-01-17  1   4   11

但是在vdate = 01-10-2020之前，我在v2movavg中应该为null。当没有空值时，rownumber> 4的平均值为5。但是，当我的一列中有n个空值时，该怎么办？

约翰

解决方法

我认为您想要的逻辑是count()：

(CASE WHEN COUNT(V2) OVER (ORDER BY VDATE ROWS BETWEEN 4 PRECEDING AND CURRENT ROW) = 5
      THEN AVG (V2) OVER (ORDER BY VDATE ASC ROWS BETWEEN 4 PRECEDING AND CURRENT ROW)
 END) AS V2MOVAVG

,

我知道您不希望在前4行中输入任何null值。您可以使用窗口计数进行测试：

case when count(v1) over(order by vdate rows between 4 preceding and current row) > 0
    then avg(v1) over(order by vdate rows between 4 preceding and current row)
end as v1movavg

这利用了count(<expr>)忽略null值的事实。