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1. |
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 join accounts. This attribute stores the primary account number. 4. Name: Name of the student 5. Hostel_Room: Room number of the hostel Which one of the following option is INCORRECT? |
A. | BankAccount_Num is candidate key |
B. | Registration_Num can be a primary key |
C. | UID is 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» B. Registration_Num can be a primary key | |