1Which of the following is the primary goal of Normalization in a Relational Database?
A.To maximize data redundancy
B.To minimize data redundancy and insertion/update/deletion anomalies
C.To create as many tables as possible
D.To ensure query performance is always maximized regardless of disk space
Correct Answer: To minimize data redundancy and insertion/update/deletion anomalies
Explanation:Normalization is a systematic approach of decomposing tables to eliminate data redundancy (repetition) and undesirable characteristics like insertion, update, and deletion anomalies.
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2If an attribute of a composite primary key determines a non-prime attribute, which normalization form is violated?
A.1NF
B.2NF
C.3NF
D.BCNF
Correct Answer: 2NF
Explanation:This describes a Partial Functional Dependency. Second Normal Form (2NF) requires that the schema be in 1NF and that no non-prime attribute is dependent on any proper subset of any candidate key.
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3Which normal form deals with the atomicity of domain values?
A.First Normal Form (1NF)
B.Second Normal Form (2NF)
C.Third Normal Form (3NF)
D.Boyce-Codd Normal Form (BCNF)
Correct Answer: First Normal Form (1NF)
Explanation:1NF requires that domains of attributes must include only atomic (indivisible) values and that the value of any attribute in a tuple must be a single value from the domain.
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4A functional dependency is considered trivial if:
A.
B.
C.
D. is a primary key
Correct Answer:
Explanation:A functional dependency is trivial if the set of attributes is a subset of (e.g., ).
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5Which of the following statements about BCNF is true?
A.Every BCNF relation is in 3NF
B.Every 3NF relation is in BCNF
C.BCNF allows transitive dependencies
D.BCNF allows partial dependencies
Correct Answer: Every BCNF relation is in 3NF
Explanation:BCNF is a stricter version of 3NF. Therefore, if a relation is in BCNF, it is automatically in 3NF, 2NF, and 1NF.
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6In the context of Armstrong's Axioms, if and , then . This rule is known as:
A.Reflexivity
B.Augmentation
C.Transitivity
D.Union
Correct Answer: Transitivity
Explanation:The Transitivity rule states that if X determines Y and Y determines Z, then X determines Z.
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7A relation is in 3NF if it is in 2NF and:
A.It has no partial dependencies
B.It has no transitive dependencies for non-prime attributes
C.It contains no multivalued dependencies
D.Every determinant is a candidate key
Correct Answer: It has no transitive dependencies for non-prime attributes
Explanation:3NF requires that no non-prime attribute is transitively dependent on the primary key.
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8Consider relation with FDs: , . The key is . Which normal form is this relation currently in?
A.1NF
B.2NF
C.3NF
D.BCNF
Correct Answer: 2NF
Explanation:It is in 2NF because is the single key, so no partial dependencies exist. However, and implies a transitive dependency via . Thus, it violates 3NF.
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9Which normal form addresses the issue of Multivalued Dependencies (MVD)?
A.3NF
B.BCNF
C.4NF
D.5NF
Correct Answer: 4NF
Explanation:Fourth Normal Form (4NF) applies to relations that contain multivalued dependencies. A relation is in 4NF if it is in BCNF and contains no non-trivial multivalued dependencies.
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10Fifth Normal Form (5NF) deals with which of the following?
A.Functional Dependencies
B.Multivalued Dependencies
C.Join Dependencies
D.Domain-Key Normal Form
Correct Answer: Join Dependencies
Explanation:5NF, also known as Project-Join Normal Form (PJNF), deals with cases where information can be reconstructed from smaller pieces that can be maintained with less redundancy (Join Dependencies).
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11What is a spurious tuple?
A.A tuple that contains NULL values
B.A tuple created by joining two tables that does not represent a valid fact in the real world
C.A duplicate tuple in a relation
D.A tuple that violates domain constraints
Correct Answer: A tuple created by joining two tables that does not represent a valid fact in the real world
Explanation:Spurious tuples are invalid records created when performing a natural join on decomposed tables if the decomposition was lossy (not lossless).
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12Which integrity rule states that no primary key attribute can be NULL?
A.Referential Integrity
B.Entity Integrity
C.Domain Integrity
D.Key Integrity
Correct Answer: Entity Integrity
Explanation:The Entity Integrity rule states that the primary key of a relation cannot contain NULL values because the primary key is used to uniquely identify individual tuples.
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13A functional dependency holds in a relation if:
A.For every tuple, the value of is unique
B.Whenever two tuples agree on , they also agree on
C.Whenever two tuples agree on , they also agree on
D. is a subset of
Correct Answer: Whenever two tuples agree on , they also agree on
Explanation:This is the formal definition of functional dependency. If , then .
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14Which of the following is NOT a pitfall in Relational Database Design?
A.Redundancy
B.Update Anomalies
C.Loss of functional dependencies during decomposition
D.Lossless Join Decomposition
Correct Answer: Lossless Join Decomposition
Explanation:Lossless Join Decomposition is a desirable property, not a pitfall. Pitfalls include redundancy, anomalies, lossy joins, and loss of dependencies.
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15Given the relation and FDs: , , and . What is the closure of attributes ?
A.
B.
C.
D.
Correct Answer:
Explanation:1. Start with . 2. Use : add . 3. Use : add . The closure includes all attributes.
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16In BCNF, for every non-trivial functional dependency , must be:
A.A composite key
B.A super key
C.A partial key
D.A foreign key
Correct Answer: A super key
Explanation:The definition of BCNF states that for every non-trivial FD , must be a super key (or candidate key).
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17Which symbol represents a Multivalued Dependency?
A.
B.
C.
D.
Correct Answer:
Explanation:The double arrow is the standard notation for Multivalued Dependencies.
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18A decomposition of a relation into and is lossless if:
A.
B.
C. or
D. contains more tuples than
Correct Answer: or
Explanation:A decomposition is lossless if the common attributes (intersection) between the decomposed relations form a super key for at least one of the decomposed relations.
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19If a relation is in 3NF but not in BCNF, what specific condition exists?
A.There is a partial dependency
B.There is a transitive dependency involving non-prime attributes
C.There is a non-trivial dependency where is not a super key and is a prime attribute
D.There are repeating groups
Correct Answer: There is a non-trivial dependency where is not a super key and is a prime attribute
Explanation:3NF allows if is a prime attribute (part of a candidate key), even if is not a super key. BCNF does not allow this.
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20Referential Integrity is essentially ensuring:
A.That every primary key is unique
B.That foreign key values match primary key values in the related table or are NULL
C.That data types match in columns
D.That no transitive dependencies exist
Correct Answer: That foreign key values match primary key values in the related table or are NULL
Explanation:Referential integrity ensures relationships between tables remain consistent. A foreign key must refer to a valid existing primary key in the parent table.
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21Which of the following is an Update Anomaly?
A.Ideally, data should be updated in one place, but due to redundancy, multiple rows must be updated to maintain consistency
B.Unable to insert data because a primary key value is missing
C.Losing legitimate data when deleting a row
D.Creating spurious tuples during join
Correct Answer: Ideally, data should be updated in one place, but due to redundancy, multiple rows must be updated to maintain consistency
Explanation:An update anomaly occurs when the same data exists in multiple places (redundancy), requiring multiple updates to ensure consistency, failing which leads to inconsistent data.
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22Data Integrity Rules primarily ensure:
A.Data security and encryption
B.Data accuracy and consistency
C.Data compression
D.Fast data retrieval
Correct Answer: Data accuracy and consistency
Explanation:Integrity constraints (Entity, Referential, Domain, etc.) are designed to keep the data accurate, valid, and consistent within the database.
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23A relation scheme is in 2NF. It has a composite Primary Key and a non-prime attribute . Which of the following dependencies would violate 2NF?
A.
B.
C.
D.
Correct Answer:
Explanation:2NF forbids partial dependencies. Since the key is , a dependency implies that depends only on part of the key (), violating 2NF.
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24Armstrong's axiom of Augmentation states that if , then:
A.
B.
C.
D.
Correct Answer:
Explanation:Augmentation states that if , adding attributes to both sides preserves the dependency ().
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25A table containing a column with a list of comma-separated phone numbers violates which form?
A.1NF
B.2NF
C.3NF
D.4NF
Correct Answer: 1NF
Explanation:1NF disallows repeating groups or multi-valued attributes within a single cell. Each column must hold an atomic value.
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26Which statement implies that a relation is definitely in BCNF?
A.It is in 3NF and has no composite candidate keys
B.It is in 3NF and has at least one foreign key
C.It has only one candidate key
D.It is a binary relation (has only 2 attributes)
Correct Answer: It is a binary relation (has only 2 attributes)
Explanation:Any binary relation (relation with exactly two attributes) is always in BCNF.
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27In the context of 4NF, a multivalued dependency is trivial if:
A. or is the whole relation scheme
B. is a proper subset of
C. is not empty
D. is a single attribute
Correct Answer: or is the whole relation scheme
Explanation:A MVD is trivial if is a subset of or if the union of and covers all attributes in the relation.
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28What is the result of decomposing a relation into using 5NF?
A.Elimination of all functional dependencies
B.Elimination of all join dependencies not implied by candidate keys
C.Removal of primary keys
D.Creation of a universal relation
Correct Answer: Elimination of all join dependencies not implied by candidate keys
Explanation:5NF ensures that there are no join dependencies that do not follow from the candidate keys of the relation.
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29Which of the following describes a Deletion Anomaly?
A.Data is lost because the database crashes
B.When a record is deleted, other useful data stored in that record is unintentionally lost
C.A record cannot be deleted because of a foreign key constraint
D.Deleting a record takes too much time
Correct Answer: When a record is deleted, other useful data stored in that record is unintentionally lost
Explanation:A deletion anomaly happens when deleting a specific fact (like an employee leaving) causes the deletion of entirely different, valid information (like the department details they worked for) because they are stored in the same tuple.
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30An attribute is called a prime attribute if:
A.It is unique for every tuple
B.It is a member of some candidate key
C.It is an integer
D.It is a foreign key
Correct Answer: It is a member of some candidate key
Explanation:Prime attributes are those that are part of any candidate key of the relation.
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31Dependency Preservation in normalization means:
A.We can enforce all original FDs by examining the individual decomposed relations without joining them
B.All dependencies are removed
C.Only primary key dependencies are kept
D.Dependencies are stored in a separate table
Correct Answer: We can enforce all original FDs by examining the individual decomposed relations without joining them
Explanation:A decomposition preserves dependencies if the union of the FDs of the decomposed relations is equivalent to the FDs of the original relation.
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32If a relation has no functional dependencies where is not a super key, it is in:
A.2NF
B.3NF
C.BCNF
D.1NF
Correct Answer: BCNF
Explanation:This describes the core condition of Boyce-Codd Normal Form: every determinant must be a super key.
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33Which of the following is FALSE regarding Armstrong's Axioms?
A.They are sound (do not generate incorrect FDs)
B.They are complete (can generate all implied FDs)
C.Pseudo-transitivity is a derived rule
D.Reflexivity only applies to primary keys
Correct Answer: Reflexivity only applies to primary keys
Explanation:Reflexivity () applies to any set of attributes, not just primary keys.
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34Consider with FDs: , , . What is the candidate key?
A.
B.
C.
D.
Correct Answer:
Explanation:To determine all attributes: gives and . gives . Neither nor appear on the right side of any dependency, so they must be in the key. . Thus, is the candidate key.
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35The concept of Join Dependency (JD) is denoted as:
A.
B.
C.
D.
Correct Answer:
Explanation:A Join Dependency, denoted , specifies that the relation is equal to the join of its projections .
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36Which normal form allows relation decomposition to be always lossless and dependency preserving?
A.BCNF
B.3NF
C.4NF
D.5NF
Correct Answer: 3NF
Explanation:It is always possible to decompose a relation into 3NF while preserving dependencies and ensuring a lossless join. BCNF guarantees lossless join but may not preserve dependencies.
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37A relation schema is defined to be in Fourth Normal Form (4NF) if, for every non-trivial multivalued dependency :
A. is a super key of
B. is a prime attribute
C. is a subset of
D. determines functionally
Correct Answer: is a super key of
Explanation:4NF requires that for every non-trivial MVD , must be a super key.
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38In the context of 4NF, MVDs arise when:
A.Two or more independent multivalued facts are stored in the same table about the same entity
B.A transitive dependency exists
C.A partial dependency exists
D.The primary key is simple
Correct Answer: Two or more independent multivalued facts are stored in the same table about the same entity
Explanation:MVDs (and the need for 4NF) occur when independent multi-valued attributes (e.g., an employee's multiple projects and multiple hobbies) are stored in a single table, creating redundancy.
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39Which of the following is a symptom of a Lossy (or Loss-full) Decomposition?
A.
B. (contains spurious tuples)
C.
D.The table size decreases
Correct Answer: (contains spurious tuples)
Explanation:A lossy decomposition results in spurious tuples when joined back together. The joined relation contains more tuples than the original relation, meaning valid association information is lost (ironically called lossy despite having more rows).
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40The rule allows us to determine if we know:
A.Any value of
B.The value of
C.The value of a third attribute
D.The count of tuples
Correct Answer: The value of
Explanation:Functional Dependency means functionally determines . If you know , you can uniquely determine .
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41If a relation is in BCNF, does it guarantee that it is free of all anomalies?
A.Yes, absolutely
B.No, it might still have anomalies due to MVDs or JDs
C.No, because BCNF allows partial dependencies
D.Yes, because BCNF is the highest normal form
Correct Answer: No, it might still have anomalies due to MVDs or JDs
Explanation:BCNF handles functional dependencies. However, anomalies can still arise from Multivalued Dependencies (addressed in 4NF) or Join Dependencies (addressed in 5NF).
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42The property that guarantees is:
A.Dependency Preservation
B.Lossless Join Property
C.Atomicity
D.Isolation
Correct Answer: Lossless Join Property
Explanation:This equation states that joining the projections of the relation recovers the original relation exactly, which is the definition of Lossless Join.
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43Consider a relation Enrollment(Student, Course, Instructor). A student takes a course, and a course can be taught by multiple instructors, but a student is assigned one specific instructor for a course. FDs: . If we also have . Which normal form is violated?
A.3NF
B.BCNF
C.2NF
D.1NF
Correct Answer: BCNF
Explanation:Candidate keys are and . The dependency exists. is a determinant but not a super key (it can't determine Student). Thus, BCNF is violated.
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44When checking for 2NF, we primarily look at:
A.Relations with composite primary keys
B.Relations with single-attribute primary keys
C.Relations with no primary keys
D.Relations with only foreign keys
Correct Answer: Relations with composite primary keys
Explanation:Partial dependencies (violating 2NF) can only occur if the primary key is composite (composed of multiple attributes). If the key is a single attribute, partial dependency is impossible.
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45Which of the following describes the Union rule of Armstrong's Axioms?
A.If and , then
B.If and , then
C.If , then
D.If , then
Correct Answer: If and , then
Explanation:The Union rule allows combining the right-hand sides of two FDs that share the same determinant (left-hand side).
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46What is the canonical cover of a set of functional dependencies?
A.A simplified set of FDs that is equivalent to the original set, free of extraneous attributes and redundant FDs
B.The set of all possible FDs implied by the original set
C.The set of all super keys
D.The set of prime attributes
Correct Answer: A simplified set of FDs that is equivalent to the original set, free of extraneous attributes and redundant FDs
Explanation:A canonical cover (or minimal cover) is the smallest, simplified version of the FD set that preserves the same closure.
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47Which normal form deals with cyclic dependencies among three or more attributes in a composite key?
A.2NF
B.3NF
C.4NF
D.5NF
Correct Answer: 5NF
Explanation:5NF deals with Join Dependencies that are often associated with cyclic constraints where a relation cannot be decomposed into two, but can be decomposed into three or more smaller relations.
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48Domain constraints specify:
A.Relationships between tables
B.Uniqueness of rows
C.Valid set of values for an attribute
D.Functional dependencies
Correct Answer: Valid set of values for an attribute
Explanation:Domain constraints ensure that the data entered into a column matches the defined data type, format, or range (e.g., Age must be an integer > 0).
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49If we have a relation and , this implies:
A.
B.
C.
D. is definitely true
Correct Answer:
Explanation:In a relation with attributes , MVDs come in pairs. If multivalued-determines , and is the rest of the attributes, then must also multivalued-determine .
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50Pitfalls in database design such as redundancy lead to inconsistency primarily because:
A.Storage is expensive
B.It is difficult to maintain the same value for a data item in multiple places during updates
C.SQL queries become too short
D.Primary keys cannot be defined
Correct Answer: It is difficult to maintain the same value for a data item in multiple places during updates
Explanation:When data is redundant, updating a logical fact requires updating multiple physical records. Failing to update all copies results in data inconsistency.
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