C175 DATA MANAGEMENT -
FOUNDATIONS COMPREHENSIVE
EXAM QUESTIONS WITH VERIFIED
ANSWERS AND DETAILED
EXPLANATIONS. 2026/2027
1. Which of the following best describes the difference between a Primary Key and a Unique
Key in a relational database?
A. A Primary Key cannot contain NULL values, whereas a Unique Key can contain at most
one NULL value (depending on the RDBMS).
B. A Primary Key allows for one NULL value, whereas a Unique Key allows for multiple
NULL values.
C. A table can have multiple Primary Keys but only one Unique Key.
D. Unique Keys are used for indexing, while Primary Keys are only used for establishing
relationships.
Answer: A
,Conceptual Explanation: A Primary Key uniquely identifies a record and strictly prohibits
NULL values. A Unique Key also ensures uniqueness but may permit a single NULL value in
many relational systems.
2. In the context of the Three-Schema Architecture, which level describes how data is actually
stored on disks?
A. Internal Level
B. Conceptual Level
C. External Level
D. Logical Level
Answer: A
Conceptual Explanation: The Internal Level (or Physical Level) describes the physical
storage structure and access paths of the database.
3. A database table is in First Normal Form (1NF) if which of the following conditions is met?
A. All attributes contain only atomic values and there are no repeating groups.
B. Every non-key attribute is fully functionally dependent on the primary key.
C. There are no transitive dependencies between non-key attributes.
D. The table has a composite key consisting of at least two columns.
Answer: A
, Conceptual Explanation: 1NF requires that all column values are atomic (indivisible) and
that the table contains no repeating groups or multi-valued attributes.
4. Which SQL clause is used to filter the results of an aggregate function after the rows have
been grouped?
A. WHERE
B. ORDER BY
C. HAVING
D. GROUP BY
Answer: C
Conceptual Explanation: The HAVING clause is specifically designed to filter groups based
on aggregate results (like SUM or COUNT), whereas WHERE filters individual rows before
grouping.
5. In an Entity-Relationship Diagram (ERD), what does a ‘Crow’s Foot’ notation represent
regarding cardinality?
A. Zero to one
B. Many
C. One and only one
D. Exactly two
Answer: B
FOUNDATIONS COMPREHENSIVE
EXAM QUESTIONS WITH VERIFIED
ANSWERS AND DETAILED
EXPLANATIONS. 2026/2027
1. Which of the following best describes the difference between a Primary Key and a Unique
Key in a relational database?
A. A Primary Key cannot contain NULL values, whereas a Unique Key can contain at most
one NULL value (depending on the RDBMS).
B. A Primary Key allows for one NULL value, whereas a Unique Key allows for multiple
NULL values.
C. A table can have multiple Primary Keys but only one Unique Key.
D. Unique Keys are used for indexing, while Primary Keys are only used for establishing
relationships.
Answer: A
,Conceptual Explanation: A Primary Key uniquely identifies a record and strictly prohibits
NULL values. A Unique Key also ensures uniqueness but may permit a single NULL value in
many relational systems.
2. In the context of the Three-Schema Architecture, which level describes how data is actually
stored on disks?
A. Internal Level
B. Conceptual Level
C. External Level
D. Logical Level
Answer: A
Conceptual Explanation: The Internal Level (or Physical Level) describes the physical
storage structure and access paths of the database.
3. A database table is in First Normal Form (1NF) if which of the following conditions is met?
A. All attributes contain only atomic values and there are no repeating groups.
B. Every non-key attribute is fully functionally dependent on the primary key.
C. There are no transitive dependencies between non-key attributes.
D. The table has a composite key consisting of at least two columns.
Answer: A
, Conceptual Explanation: 1NF requires that all column values are atomic (indivisible) and
that the table contains no repeating groups or multi-valued attributes.
4. Which SQL clause is used to filter the results of an aggregate function after the rows have
been grouped?
A. WHERE
B. ORDER BY
C. HAVING
D. GROUP BY
Answer: C
Conceptual Explanation: The HAVING clause is specifically designed to filter groups based
on aggregate results (like SUM or COUNT), whereas WHERE filters individual rows before
grouping.
5. In an Entity-Relationship Diagram (ERD), what does a ‘Crow’s Foot’ notation represent
regarding cardinality?
A. Zero to one
B. Many
C. One and only one
D. Exactly two
Answer: B
