How do I validate these columns? - sql

Question

I'm working on a database and I need to validate some columns under the Payment schema.
Like if a credit card is not used for payments, CreditCardNumber, CardHoldersName, and CreditCardExpDate should be made NULL. If a credit card is used, the CreditCardExpDate value should be greater than the PaymentDate
PaymentDue can allow NULL but should not be greater than PaymentAmount
I've searched online but what I get are complex triggers and procedures which are not really helpful.
create table Payment.Payments(
Payment_ID int identity (200, 21),
Payment_Amount money constraint chk_Payment_Amount check (Payment_Amount >
'0'),
Payment_Date date, -- is to be greater than the end date which is on another table
Credit_Card_Number int,
Card_Holders_Name char (50),
Credit_Card_Expiry_Date date,
Project_ID int Foreign Key references ProjectDetails.Projects(Project_ID),
Payment_Due money -- should not be greater than Payment Amount but
can still accept null*
);
The notes show the current validation problem i'm having.
I created a trigger for the payment_date but i can only get it to fire when the inserted date is greater than the current date, i need it to fire if it is less than the end date(end date is on another table)
CREATE TRIGGER paymentdate
ON Payment.Payments
FOR INSERT
AS
DECLARE #ModifiedDate date
SELECT #ModifiedDate = Payment_Date FROM Inserted
IF (#ModifiedDate > getdate())
BEGIN
PRINT 'The modified date should be the current date. Hence, cannot insert.'
ROLLBACK TRANSACTION
END

Answer 1

I'm reading a lot between the lines here, but I think this is what you're after (Note I have used the dbo schema though):
USE Sandbox;
GO
CREATE TABLE dbo.Payments (
Payment_ID int identity(200, 21),
Payment_Amount money CONSTRAINT chk_Payment_Amount CHECK (Payment_Amount > '0'),
Payment_Date date,
Credit_Card_Number char(19), --note datatype change from int to char. See my comment below (copied from my comment)
Card_Holders_Name varchar (50), --note I've used varchar instead. Names aren't all 50 characters long
Credit_Card_Expiry_Date date,
--Project_ID int FOREIGN KEY REFERENCES ProjectDetails.Projects(Project_ID) --Commented out as I don't have this table
Payment_Due money CONSTRAINT chk_Payment_Due CHECK (Payment_Due > '0' OR Payment_Due IS NULL)
);
GO
--Credit Card format validation
ALTER TABLE dbo.Payments ADD CONSTRAINT ck_Credit_Card CHECK (Credit_Card_Number LIKE '[0-9][0-9][0-9][0-9] [0-9][0-9][0-9][0-9] [0-9][0-9][0-9][0-9] [0-9][0-9][0-9][0-9]' OR Credit_Card_Number IS NULL);
--Add card details must be there, or none.
ALTER TABLE dbo.Payments ADD CONSTRAINT ck_Card_Details CHECK ((Credit_Card_Number IS NULL AND Card_Holders_Name IS NULL AND Credit_Card_Expiry_Date IS NULL)
OR (Credit_Card_Number IS NOT NULL AND Card_Holders_Name IS NOT NULL AND Credit_Card_Expiry_Date IS NOT NULL))
GO
DROP TABLE dbo.Payments;
Comment made on the Card Number's datatype:
The datatype int for a credit card number is a bit of an oxymoron. The maximum value for an int is 2,147,483,647 and a card number is made up of 4 sets of 4 digit numbers (i.e. 9999 9999 9999 9999). Even as a number, that's far higher than the max value of an int. I'd suggest using a char(19) and making a constraint on the format as well.