CMSC 508 Quiz 3
Evaluating the hierarchy of normal forms, which of these is a correct observation?
Every table in 2NF is also in 1NF, but the reverse is not always true.
Evaluating the normalization process, which of the following is a correct observation about 2NF?
For a relation to be in 2NF, it must first satisfy the requirements of 1NF and have no partial dependencies.
For a relation to be in BCNF, which of the following must be true?
For every non-trivial FD, the left-hand side must be a superkey.
What does Boyce-Codd Normal Form (BCNF) primarily address that 3NF might allow?
Functional dependencies where non-prime attributes determine prime attributes.
Given that X is a set of attributes and F is a set of functional dependencies, which statement correctly evaluates the closure X+ under F?
If Y is a subset of X+, then X functionally determines Y.
Which of the following is not a primary purpose of normalization?
Increase query performance.
Which of the following best evaluates the need for Functional Dependency Preservation during decomposition?
It ensures that original constraints can still be enforced after decomposition.
When analyzing the closure of a set of attributes, which statement best describes its purpose?
It identifies all attributes that can be functionally determined by the given set.
Which of the following is true regarding canonical cover?
It is a minimal set of FDs that is equivalent to the original set.
In analyzing the canonical cover of a set of functional dependencies, which of the following properties is crucial?
It is equivalent to the original set of FDs without any extraneous attributes.
Which of the following is true for a relation in 2NF?
It is free of partial dependencies on the primary key.
A relation is decomposed into R1 and R2. If joining R1 and R2 using a natural join produces spurious tuples, what might be inferred about the decomposition?
It's a lossy decomposition.
What is a primary characteristic of a canonical cover for functional dependencies in a relation?
It's a minimal set of FDs that's equivalent to the original set and has no extraneous attributes.
When breaking down a relation into smaller relations, which of the following is most crucial to avoid?
Losing data when re-joining the decomposed relations.
For a relation to be in 4NF, which type of dependency should it not contain?
Multi-valued dependencies that are not a superkey
Given a relation R(A,B,C,D) with FDs {A -> B, B -> C}, which attributes' closure includes D?
None of the given attributes' closures include D.
In relation to functional dependencies, which term describes the scenario when the intersection of two or more FDs is a non-empty set?
Overlapping FDs
In the normalization process, what would you expect to observe if an incorrect canonical cover was used?
Potential loss or misrepresentation of functional dependencies.
If a relation R is in BCNF, which of the following must also be true?
R is in 3NF
During denormalization, which of the following might be intentionally introduced for the sake of performance?
Redundant data
Given a relation R and a set of functional dependencies F, what would imply that an attribute A is extraneous in a functional dependency?
Removing A from the FD doesn't change the closure of the remaining attributes.
In the context of databases, what does "atomicity" in 1NF refer to?
The indivisibility of attribute values
Which of the following evaluations regarding the Relational Model is accurate?
The relational model uses tables (relations) to represent data and relationships.
What does the closure of an attribute set determine?
The set of all attributes that are functionally determined by it
Which of the following statements best describes the role of multi-valued dependencies (MVDs) in the normalization process?
They indicate scenarios where an attribute determines another set of attributes but not vice versa.
Which of the following might be a reason to use denormalization in a database design?
To achieve faster read operations at the cost of some redundancy.
What is the main aim of normalization algorithms?
To eliminate data redundancy and anomalies
What is the primary goal of 2NF?
To eliminate partial dependencies.
Why is denormalization sometimes used in database design?
To enhance performance
Why is Functional Dependency Preservation important in the normalization process?
To ensure that all functional dependencies of the original relation can be enforced in the decomposed relations.
When might denormalization be considered beneficial during database design?
To improve performance for specific query patterns.
In denormalization, what is typically a driving factor?
To improve query performance
When analyzing functional dependency preservation, why might a database designer opt for a design that doesn't preserve all FDs?
To strike a balance between query efficiency and normalization.
In which of the following scenarios would it be MOST appropriate to consider denormalization?
When optimizing a database for specific read-heavy use cases.
A table with repeating groups or arrays violates which of the following normal forms?
1NF
If you're given a relation where all attributes are prime attributes (part of some candidate key), which normal form is it guaranteed to be in?
2NF
Boyce-Codd Normal Form (BCNF) is a stricter version of:
3NF
If a relation is in BCNF, which other normal form is it also guaranteed to be in?
3NF
In a relation, a non-prime attribute functionally determines another non-prime attribute. This violation is against which normal form?
3NF
In which Normal Form must a relation have no transitive dependencies of non-key attributes on the primary key?
3NF
Which normal form requires removing both partial and transitive dependencies?
3NF
Which of the following best describes a partial dependency?
A dependency of an attribute on just part of a composite key.
In terms of Functional Dependency Preservation, which evaluation is true?
A lossless join decomposition that doesn't preserve FDs might require more expensive queries to enforce constraints.
Which of the following best describes a Canonical Cover?
A minimal set of functional dependencies that is equivalent to the original
What does the term "transitive dependency" in the context of databases refer to?
A non-key attribute depending on another non-key attribute.
Which of the following best defines a partial dependency?
A non-key attribute depends on part of a composite key.
Consider a database relation with a set of functional dependencies. Which situation is indicative of a transitive dependency violation of the 3NF?
A non-prime attribute determines another non-prime attribute.
In the context of the Relational Model, what does a tuple represent?
A row in a table
Given the functional dependencies {A -> B, B -> C}, which of the following closures will include A, B, and C?
A+
Consider a relation R(A, B, C, D). If {A -> C, BC -> D} are the given functional dependencies, which attribute or set of attributes is guaranteed to be a candidate key?
AB
Evaluating the following relation R(A, B, C, D) with FDs: A->B, BC->D. Which of these FDs is extraneous?
BC->D
If every non-trivial functional dependency in a relation has a superkey on its left side, the relation is in which normal form?
BCNF
Which scenario is indicative of a lossless decomposition?
Both of the above.
Which of the following evaluations regarding Canonical Cover is incorrect?
Canonical cover requires that every functional dependency has a left-hand side with multiple attributes.
Evaluating the process of determining the closure of a set of attributes, which statement is accurate?
Computing the closure helps in determining superkeys for a relation.
Given a relational database, which evaluation regarding denormalization is true?
Denormalization can improve read performance but might compromise write efficiency.
If a relation is decomposed in a way that some functional dependencies cannot be tested directly on the decomposed relations, the decomposition lacks:
Dependency Preservation Property
When decomposing a relation, which of the following properties ensures that no functional dependencies are lost?
Dependency Preservation Property
When decomposing relations for normalization, what is the primary goal concerning functional dependency preservation?
Ensure that all functional dependencies are still valid without introducing spurious tuples.
In the normalization process, which step ensures that the relationship is free of transitive dependencies on its primary key?
Ensuring 3NF
When evaluating BCNF in comparison to 3NF, which statement correctly reflects their relationship?
Every relation in BCNF is also in 3NF, but not vice versa.
