UGC NET CSE | January 2017 | Part 3 | Question: 8

Question

Which one is correct w.r.t. RDBMS?

• A. primary key $\subseteq$ super key $\subseteq$ candidate key
• B. primary key $\subseteq$ candidate key $\subseteq$ super key 
• C. super key $\subseteq$ candidate key $\subseteq$ primary key  
• D. super key $\subseteq$ primary key $\subseteq$ candidate key

Answer 1

In RDBMS there can be only one PK. We can have many Candidate Key, any of which can be chosen as PK by admin. Super key is obtained by adding zero or more attribute to candidate key.

So B is correct.

Answer 2

In the Relation There is many Super Key Out of Which some of them are Candidate key .

and there are one or more Candidate key but have only one Primary key .

so , option B is correct

Answer 3

Ans : B

 primary key ⊆ candidate key ⊆ super key in RDBMS