Question

版本1 ：我有一个“费用”表

FEE
-Id
-VariableAmount
-FixedAmount
-CurrencyCode

当执行提款时，从系统中取出的钱到用户的银行账户等，每笔交易都会收取可变金额+固定金额费用。

版本2 ：我想在满足指定条件时收取一系列费用规则，例如

Charge $0 when < $200 

Charge $3 when >= $200

Charge $x when >= $Y

我可以在我的网络应用程序中对其进行硬编码，这样可行，但我希望以后能够更改它，在数据库中存储这些条件时，您将如何设计它？

费用1. * FEE_RULE ??你在数据库中存储了什么？

Answer 1

您所描述的是规则引擎。 SQL Server没有内置的，但MSDN上有一篇文章描述了如何构建自己的文章。对于一条规则来说，它似乎有点过度设计，但也许您的应用程序也有其他规则。 Find out more.

Answer 2

您始终可以将此业务逻辑放在负责执行提款的存储过程中。这样，当您想要更改逻辑时，您不必重新部署Web应用程序。

Answer 3

我的方法，最简单的形式，如下所示。

USE tempdb
GO
IF OBJECT_ID('tempdb.dbo.Transactions') IS NOT NULL DROP TABLE Transactions

SELECT TOP 500 TxnVal = ABS(CHECKSUM(NEWID())) % 1000
INTO Transactions
FROM sys.columns

;WITH Fee (Id, VariableAmountFloor, VariableAmountCeiling, VariableAmount, FixedAmount, CurrencyCode) AS
(
    SELECT 1, 0,    200,        0.8,    0.1, 'x'    UNION ALL
    SELECT 2, 201,  300,        0.65,   0.1, 'x'    UNION ALL
    --  NB: have chosen 2147483647 as the ceiling because it is the maximum value of the INT type
    --  You will probably have some sort of float
    SELECT 3, 301,  2147483647, 0.4,    0.1, 'x'
)
SELECT   T.TxnVal
        ,VariableFee    = F.VariableAmount
        ,FixedFee       = F.FixedAmount
        ,TxnPlusCosts   = T.TxnVal + F.VariableAmount + F.FixedAmount
FROM Transactions   T
JOIN Fee            F ON T.TxnVal BETWEEN F.VariableAmountFloor AND F.VariableAmountCeiling

Answer 4

SET ANSI_WARNINGS ON;
GO

--DROP TABLE dbo.FeeInterval
CREATE TABLE dbo.FeeInterval (
    FeeIntervalID INT IDENTITY(1,1),    
        CONSTRAINT PK_FeeInterval PRIMARY KEY (FeeIntervalID),

    StartValue NUMERIC(18,2) NOT NULL,
        CONSTRAINT CK_FeeInterval_StartValue CHECK (StartValue > 0),
    -- If EndValue IS NOT NULL Then the interval is TxValue BETWEEN [StartValue, EndValue]
    -- Else (EndValue IS NULL) Then the interval is TxValue >= StartValue
    -- Also, you should check is this intervals are continuous (using a trigger)
    -- and only the last EndValue IS NULL
    EndValue NUMERIC(18,2) NULL, -- Allow null,
        CONSTRAINT CK_FeeInterval_StartDate_EndDate CHECK (StartValue < EndValue),
    VariableAmount NUMERIC(18,2) NOT NULL, 
    FixedAmount NUMERIC(18,2) NOT NULL
);
-- + CREATE INDEX ...
GO

--DROP TABLE dbo.[Transaction] 
CREATE TABLE dbo.[Transaction] (
    TransactionID INT IDENTITY(1,1),
        CONSTRAINT PK_Transaction PRIMARY KEY (TransactionID),
    TransactionDate DATE NOT NULL
        CONSTRAINT DF_Transaction_TransactionDate DEFAULT GETDATE(),
    -- You should check (using a trigger) if there is an applicable fee for this TxnValue 
    --      If the last EndValue IS NOT NULL Then TxnValue BETWEEN MIN(StartDate) AND MAX(EndValue) 
    --      Else (the last Endvalue IS NULL Then TxnValue >= MIN(StartDate)
    TxnValue NUMERIC(18,2) NOT NULL
    -- Also, you should store the FeeIntervalID used for every transaction
    -- FeeIntervalID INT NOT NULL 
    -- and (maybe) VariableAmount/FixedAmount/TxnPlusCosts NUMERIC(18,2) NOT NULL
)
GO

INSERT dbo.FeeInterval (StartValue, EndValue, VariableAmount, FixedAmount)
SELECT 0.01, 200,       0.8,    0.1    UNION ALL -- 0.01 because data type is NUMERIC(,2)
SELECT 201,  300,       0.65,   0.1    UNION ALL
SELECT 301,  NULL,      0.4,    0.1;
GO

INSERT dbo.[Transaction] (TxnValue)
SELECT 0.01 UNION ALL
SELECT 50 UNION ALL
SELECT 200 UNION ALL
SELECT 250 UNION ALL
SELECT 350 UNION ALL
SELECT -0.01; -- Wrong value
GO

--DROP FUNCTION dbo.GetApplicableFee
CREATE FUNCTION dbo.GetApplicableFee(@TxnValue NUMERIC(18,2))
RETURNS TABLE
AS
RETURN
SELECT  s.FeeIntervalID, s.VariableAmount, s.FixedAmount, @TxnValue + s.VariableAmount + s.FixedAmount AS TxnPlusCosts
FROM (
    SELECT  i.FeeIntervalID, i.VariableAmount, i.FixedAmount,
            i.StartValue, i.EndValue,
            ROW_NUMBER() OVER(ORDER BY i.StartValue DESC) RowNum
    FROM    dbo.FeeInterval i
) s
WHERE   @TxnValue BETWEEN s.StartValue AND s.EndValue AND s.RowNum > 1
OR      @TxnValue >= s.StartValue AND s.RowNum = 1
GO

SELECT  *,
        CASE WHEN f.FeeIntervalID IS NOT NULL THEN 'TxnValue with applicable fee' ELSE 'Wrong TxnValue' END AS [Description]
FROM    dbo.[Transaction] txn
OUTER APPLY dbo.GetApplicableFee(txn.TxnValue) f
-- or
SELECT  *, 
        (SELECT f.TxnPlusCosts FROM dbo.GetApplicableFee(txn.TxnValue) f) AS TxnPlusCosts
FROM    dbo.[Transaction] txn

如果您有任何疑问，请随时提出。

Answer 5

我认为您可以使用oracle过滤器表达式来实现您通过数据库建议的内容而无需更改应用程序... 本教程将帮助您实现此目的 http://docs.oracle.com/cd/B12037_01/server.101/b10821/expressionconcepts.htm

数据库设计 - 存储条件规则？

5 个答案: