Question

Match LIST-I with LIST-II
LIST-I
(A) Primary Key
(B) Alternate Key
(C) Super Key
(D) Composite Key
LIST-II
(I) Composed with at least two attributes
(II) Can contain extraneous attributes
(III) Only one such key is permitted in a relation
(IV) Used when the primary key is not working

• A. A - I, B - II, C - III, D - IV
• B. A - III, B - IV, C - I, D - II
• C. A - I, B - II, C - IV, D - III
• D. A - III, B - IV, C - II, D - I

Hint:

Key Hierarchy: Super Key > Candidate Key. - Super Key: Any set of attributes that uniquely identifies a row. - Candidate Key: A minimal Super Key. - Primary Key: The chosen Candidate Key. - Alternate Key: A Candidate Key that is not the Primary Key. - Composite Key: A key made of more than one attribute.

Answer 1

The Correct Option is D

Step 1: Analyze Primary Key (A)
A primary key is a candidate key chosen to uniquely identify each record in a table. A table (relation) can have only one primary key. Thus, A matches with (III).

Step 2: Analyze Alternate Key (B)
A table can have multiple candidate keys. One is chosen as the primary key. The remaining candidate keys are called alternate keys. The description (IV) is poorly phrased, but it likely refers to these other candidate keys. Thus, B matches with (IV).

Step 3: Analyze Super Key (C)
A super key is a set of one or more attributes that, taken collectively, can uniquely identify a record. A candidate key is a minimal super key (no attribute can be removed). Therefore, a super key can contain extra, non-essential attributes. Thus, C matches with (II).

Step 4: Analyze Composite Key (D)
A composite key is a key that consists of two or more attributes to uniquely identify a record. It is a key composed of at least two attributes. Thus, D matches with (I). Conclusion: The matching is A-III, B-IV, C-II, D-I.