Question

I’m currently doing a banking website for my project, using C# and asp.net. One of the function is ‘Remaining Daily Limit’. I need the database value to change back to default once I changed the system date to another day. Example : If a user had $500 (default value) as a daily limit, and he used all up. The next day, he will have $500 again. May I know how should I go about it?

Answer 1

Here is a SQL script that will create how I would setup your db with some sample data:

CREATE TABLE tblBankCustomer
(
    BankCustomerId INT NOT NULL IDENTITY(1,1) PRIMARY KEY
    , FirstName NVARCHAR(100) NOT NULL
    , LastName NVARCHAR(100) NOT NULL
    , DailySpendingLimit DECIMAL(38, 2) NOT NULL CONSTRAINT DF_tblBankCustomer_DailySpendingLimit DEFAULT(500)
)

CREATE TABLE tblTransactionType
(
    TransactionTypeId INT NOT NULL IDENTITY(1,1) PRIMARY KEY
    , TransactionType VARCHAR(50) NOT NULL
)

INSERT tblTransactionType (TransactionType)
VALUES ('Deposit')
    , ('Withdrawal')

CREATE TABLE tblTransaction
(
    TransactionId INT NOT NULL IDENTITY(1,1) PRIMARY KEY
    , BankCustomerId INT NOT NULL
    , TransactionDate DATE NOT NULL
    , Amount DECIMAL(38, 2) NOT NULL
    , TransactionTypeId INT NOT NULL
)

ALTER TABLE tblTransaction
ADD CONSTRAINT FX_tblTransaction_tblBankCustomer
FOREIGN KEY (BankCustomerId)
REFERENCES tblBankCustomer(BankCustomerId)

ALTER TABLE tblTransaction
ADD CONSTRAINT FX_tblTransaction_tblTransactionType
FOREIGN KEY (TransactionTypeId)
REFERENCES tblTransactionType(TransactionTypeId)

INSERT tblBankCustomer
(
    FirstName
    , LastName
)
VALUES ('Jeremy', 'Pridemore')
    , ('K', 'YQ')

INSERT tblTransaction
(
    BankCustomerId
    , TransactionDate
    , Amount
    , TransactionTypeId
)
VALUES
    (1, CURRENT_TIMESTAMP, 48.50, 2) -- Jeremy, Today, $48.50, Withdrawal
    , (1, CURRENT_TIMESTAMP, 300.00, 2) -- Jeremy, Today, $300, Withdrawal
    , (1, CURRENT_TIMESTAMP, -200.00, 1) -- Jeremy, Today, $200, Deposit
    , (2, CURRENT_TIMESTAMP, 285.00, 2) -- K, Today, $285, Withdrawal
    , (2, CURRENT_TIMESTAMP, 215.00, 2) -- K, Today, $215, Withdrawal
GO
CREATE FUNCTION fGetRemainingSpendingLimit
(
    @BankCustomerId INT
    , @Date DATE
)
RETURNS DECIMAL(38, 2)
BEGIN
    SET @Date = ISNULL(@Date, CURRENT_TIMESTAMP)

    DECLARE @RemainingLimit DECIMAL(38, 2) =
    (SELECT
        SUM([Transaction].Amount)
    FROM tblBankCustomer Customer
    INNER JOIN tblTransaction [Transaction]
        ON [Transaction].BankCustomerId = Customer.BankCustomerId
        AND [Transaction].TransactionDate = @Date
    INNER JOIN tblTransactionType TransactionType
        ON TransactionType.TransactionTypeId = [Transaction].TransactionTypeId
        AND TransactionType.TransactionType = 'Withdrawal'
    WHERE Customer.BankCustomerId = @BankCustomerId)

    RETURN @RemainingLimit
END
GO

-- Some sample selects
SELECT dbo.fGetRemainingSpendingLimit(1, NULL)
SELECT dbo.fGetRemainingSpendingLimit(2, NULL)

Then in C# you should know the customer’s ID for the customer you’re working with. If you’re using somethiing like ADO.NET you can call this function directly and use the value in code.