Question:
Which of the following can uniquely identify the tuples of a relation in a database?
(A) Foreign Key
(B) Primary Key
(C) Candidate Key
(D) Composite Primary Key
Choose the correct answer from the options given below:
Which of the following can uniquely identify the tuples of a relation in a database?
(A) Foreign Key
(B) Primary Key
(C) Candidate Key
(D) Composite Primary Key
Choose the correct answer from the options given below:
(A) Foreign Key
(B) Primary Key
(C) Candidate Key
(D) Composite Primary Key
Choose the correct answer from the options given below:
Show Hint
Foreign keys establish cross-table links and can have duplicate or NULL entries in the referencing table.
Only Super, Candidate, and Primary (simple or composite) keys guarantee uniqueness of tuples within their own table.
Only Super, Candidate, and Primary (simple or composite) keys guarantee uniqueness of tuples within their own table.
Updated On: Sep 7, 2026
- (A), (B) and (D) only
- (A), (C) and (D) only
- (A), (B), (C) and (D)
- (B), (C) and (D) only
Show Solution
Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Concept:
Relational database relations are based on set theory, requiring that each tuple within a relation must be unique.
To distinguish each tuple uniquely from all others, certain attributes or attribute sets are designated as candidate, primary, or composite keys.
Step 1: Evaluation of Candidate and Primary Keys:
A Candidate Key is a minimal set of attributes that can uniquely identify any tuple in a relation without redundancy.
A Primary Key is chosen by the database designer from among the candidate keys to serve as the official unique identifier for each record.
A Composite Primary Key is a primary key that consists of two or more attributes combined together to achieve unique tuple identification.
Hence, (B), (C), and (D) all inherently possess the unique identification property.
Step 2: Evaluation of Foreign Key:
A Foreign Key is an attribute or collection of attributes in one relation that refers to the primary key of another relation.
A foreign key is allowed to contain duplicate values (for example, multiple employees having the same department ID) and null values unless restricted.
Consequently, a foreign key does not guarantee unique identification of tuples within its own host relation.
Final Answer:
The keys that can uniquely identify the tuples are Primary Key, Candidate Key, and Composite Primary Key, which corresponds to (B), (C), and (D) only.
Relational database relations are based on set theory, requiring that each tuple within a relation must be unique.
To distinguish each tuple uniquely from all others, certain attributes or attribute sets are designated as candidate, primary, or composite keys.
Step 1: Evaluation of Candidate and Primary Keys:
A Candidate Key is a minimal set of attributes that can uniquely identify any tuple in a relation without redundancy.
A Primary Key is chosen by the database designer from among the candidate keys to serve as the official unique identifier for each record.
A Composite Primary Key is a primary key that consists of two or more attributes combined together to achieve unique tuple identification.
Hence, (B), (C), and (D) all inherently possess the unique identification property.
Step 2: Evaluation of Foreign Key:
A Foreign Key is an attribute or collection of attributes in one relation that refers to the primary key of another relation.
A foreign key is allowed to contain duplicate values (for example, multiple employees having the same department ID) and null values unless restricted.
Consequently, a foreign key does not guarantee unique identification of tuples within its own host relation.
Final Answer:
The keys that can uniquely identify the tuples are Primary Key, Candidate Key, and Composite Primary Key, which corresponds to (B), (C), and (D) only.
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