Q. 12 Consider a relational table with a single record for each registered student with
the following attributes.
1. Registration_Num: Unique registration number of each registered student
2. UID: Unique identity number, unique at the national level for each citizen
3. BankAccount_Num: Unique account number at the bank. A student can
have multiple accounts or joint accounts. This attribute stores the primary
account number.
4. Name: Name of the student
5. Hostel_Room: Room number of the hostel
Which of the following options is INCORRECT?
(A) BankAccount_Num is a candidate key
(B) Registration_Num can be a primary key
(C) UID is a candidate key if all students are from the same country
(D) If S is a superkey such that S+UID is NULL then S,UID is also a
superkey
Answer: (A)
Explanation:
