如何递归地处理输入集

Question

在sql server 2008 r2上工作，在递归计费量计算过程中需要帮助。想写一个sp，在我的sp中我需要根据参数头和给定量来计算头总和： 图片描述我的数据库输入集，从输入集我需要计算给定头上的总电荷量，

我的表格脚本：

CREATE TABLE [dbo].[testCharge](
    [Head] [int] NULL,
    [Amount] [decimal](18, 6) NULL,
    [IsPercent] [bit] NULL,
    [Head Percent] [int] NULL
) ON [PRIMARY]
GO
INSERT [dbo].[testCharge] ([Head], [Amount], [IsPercent], [Head Percent]) VALUES (100, CAST(10.000000 AS Decimal(18, 6)), 1, 103)
INSERT [dbo].[testCharge] ([Head], [Amount], [IsPercent], [Head Percent]) VALUES (101, CAST(10.000000 AS Decimal(18, 6)), 1, 102)
INSERT [dbo].[testCharge] ([Head], [Amount], [IsPercent], [Head Percent]) VALUES (102, CAST(50.000000 AS Decimal(18, 6)), 0, NULL)
INSERT [dbo].[testCharge] ([Head], [Amount], [IsPercent], [Head Percent]) VALUES (103, CAST(20.000000 AS Decimal(18, 6)), 1, 101)

使用下面的语法来检索值，这里的问题是如何在CTE上计算。

DECLARE @HeadID INT = 103 ;
WITH    MyCTE
          AS ( 

          ---get base
                SELECT   Head ,
                        [Head Percent] ,
                        IsPercent ,
                        Amount
               FROM     testCharge
               WHERE    Head = @HeadID



               UNION ALL
               --get base related records
               SELECT   charge.Head ,
                        charge.[Head Percent] ,
                        charge.IsPercent ,
                        charge.Amount
               FROM     MyCTE cte
                        INNER JOIN testCharge charge ON cte.[Head Percent] = charge.Head

             )
    SELECT  *
    FROM    MyCTE

假设：

for my inputset-1 my head parameter is Utility and given amount is 400 sp return 10

for my inputset-2 my head parameter is Wages and given amount is 800 sp return 11

for my inputset-3 my head parameter is Utility and given amount is 500 sp return 56.1

如何递归处理输入集。

注意：我的输入已在DB中，无需考虑输入集。