The Internet café must keep records of the users and be able to charge users for the time that they were logged onto the Internet - NSC Information Technology - Question 4 - 2016 - Paper 2

One way to indicate the format for entering time is by using two combo boxes; one for selecting hours (0-23) and another for minutes (0-59). This would guide the user toward entering a valid time format without altering the existing label.

Valid data refers to data that fits within the established rules, such as a time value that is within the range of 0 to 24 hours. Correct data, on the other hand, refers to data that accurately reflects the real-world value; for example, if a user enters '25:00' as the time, it is valid (within the range) but incorrect as it does not represent a legitimate time.

The tblComputers table has a unique identifier for each computer, 'ComputerNumber', that can serve as a primary key. The tblUsers table should have a foreign key that references this 'ComputerNumber' to create a one-to-many relationship, where one computer can be associated with multiple users.

The SQL code to retrieve the logout time for users who paid with debit cards is as follows:

SELECT LogoutTime
FROM tblUsers
WHERE PaymentMethod = 'Debit Card'
ORDER BY LogoutTime;

The SQL code to update the payment method is:

UPDATE tblUsers
SET PaymentMethod = 'Credit Card'
WHERE UserIDNo = '73110117564076';

The SQL code to count the number of users who paid with cash is:

SELECT COUNT(UserIDNo) AS CountCashIds
FROM tblUsers
WHERE PaymentMethod = 'Cash';

The SQL code to display users logged in after 12:00 on a specific date is:

SELECT *
FROM tblUsers
WHERE (LoginTime > '12:00')
AND (LoginDate = '2016/02/25');

An audit trail captures essential information such as:

1. Records of actions performed on the database (e.g., insertions, deletions, updates).
2. User identity who made changes to the database.
3. Timestamp of when changes were made.

Data can be captured invisibly through methods such as:

1. Using credit cards or loyalty cards during purchases, which records transaction data automatically.
2. Tracking user activity when browsing websites, allowing for data collection without user consent being explicitly required.

The process of using sophisticated software to determine patterns in data statistically is called 'Data Mining'.