ALTER TRIGGER CustomerProtect
ON tblCustomer
AFTER UPDATE
AS
--Checks if a customer address has been provided in the update statement.
IF EXISTS (SELECT CustomerAddress FROM inserted WHERE CustomerAddress = '')
BEGIN
    PRINT ('Error: Please provide a Customer Address to allow this update to continue.')
    ROLLBACK TRANSACTION
END
--Checks if a customer postcode has been provided in the update statement.
ELSE
IF EXISTS (SELECT CustomerPostcode FROM inserted WHERE CustomerPostcode = '')
BEGIN
    PRINT ('Error: Please provide a Customer Postcode to allow this update to continue.')
    ROLLBACK TRANSACTION
END
--Prevents the customer names from being updated.
ELSE
IF EXISTS (SELECT CustomerName FROM inserted WHERE CustomerName <> (SELECT CustomerName FROM deleted)) --WHERE CustomerName = ' ') --<> (SELECT CustomerName FROM deleted))
BEGIN
    PRINT ('Error Names cannot be updated.')
    ROLLBACK TRANSACTION
END
ELSE
BEGIN
--Inserts the old data into the Audit table.
    INSERT INTO tblNewAudit ([Identification], [DATE], [CustName], [CustomerAddressOld],[CustomerPostcodeOld])
    SELECT USER, CURRENT_TIMESTAMP, CustomerName, CustomerAddress, CustomerPostcode FROM deleted
--Updates the number of previous addresses column in the customer table.
    UPDATE tblCustomer SET [PreviousAddressNumber] += '1' WHERE CustomerName = (SELECT CustomerName FROM deleted)
    SELECT * FROM [dbo].[tblNewAudit]
    PRINT ('COMPLETED')
END