Question

我正在使用MS SQL Server，并且具有下表'tmp_AVG_Weekly_Sales'：

RowID   SKU   Shop  Week   Avg_Value   LAMBDA    PMF      Value
  1     ABC   200    2       1          2        0.13     NULL
  2     DEF   250    2       2          4        0.018    NULL
  3     XYZ   300    3       3          6        0.0024   NULL

我需要根据以下逻辑计算出Value字段-我正在使用游标和循环：

DECLARE @CUMULATIVE AS FLOAT = 0;
DECLARE @COUNT AS INT = 0;
DECLARE @LAMBDA AS FLOAT;
DECLARE @RowID AS INT;
DECLARE @PoissonCursor AS CURSOR;
DECLARE @THRESHOLD AS FLOAT = 0.99;
DECLARE @PMF AS FLOAT --= EXP(-@LAMBDA)


SET @PoissonCursor = CURSOR FOR

SELECT RowID
FROM 
[tmp_AVG_Weekly_Sales]

OPEN @PoissonCursor;

FETCH NEXT FROM @PoissonCursor INTO @RowID;

WHILE @@FETCH_STATUS = 0

BEGIN

    SELECT @LAMBDA = LAMBDA FROM [tmp_AVG_Weekly_Sales] WHERE RowID = @RowID

    SELECT @PMF = PMF FROM [tmp_AVG_Weekly_Sales] WHERE RowID = @RowID

    WHILE (@CUMULATIVE < @Threshold)

    BEGIN
        SET @CUMULATIVE += @PMF
        SET @COUNT += 1
        SET @PMF = @PMF * (@LAMBDA / @COUNT)

        END

        UPDATE [tmp_AVG_Weekly_Sales] SET [Value] = @COUNT - 1 WHERE RowID = @RowID

    FETCH NEXT FROM @PoissonCursor  INTO @RowID;

END

但是，以上只是用相同的值填充“值”字段：

RowID   SKU   Shop  Week   Avg_Value   LAMBDA    PMF      Value
  1     ABC   200    2       1          2        0.13     6
  2     DEF   250    2       2          4        0.018    6
  3     XYZ   300    3       3          6        0.0024   6

当我期望以下内容时：

RowID   SKU   Shop  Week   Avg_Value   LAMBDA    PMF      Value
  1     ABC   200    2       1          2        0.13     6
  2     DEF   250    2       2          4        0.018    9
  3     XYZ   300    3       3          6        0.0024   12

我要去哪里错了？

Answer 1

您永远不会重置@CUMULATIVE或增加@Threshold，因此SET调用的块仅在第一次执行时执行，而随后的每个UPDATE仅使用那些原始值。

T SQL游标仅更新具有相同值的行

1 个答案: