Podcast
Questions and Answers
Which term is used to denote a functional dependency from X to Y?
Which term is used to denote a functional dependency from X to Y?
- Dependent Relation
- Functional Determination (correct)
- Function Denial
- Dependency Indication
In the relation Account(ano, balance, bname), which attribute fully functionally depends on 'ano'?
In the relation Account(ano, balance, bname), which attribute fully functionally depends on 'ano'?
- Ano
- No attributes fully functionally depend on 'ano' (correct)
- Bname
- Balance
What does FD stand for in the context of Functional Dependency?
What does FD stand for in the context of Functional Dependency?
- Function Definition
- Functional Determinant
- Functional Dependency (correct)
- Fully Determined
Which side of a Functional Dependency is referred to as the determinant?
Which side of a Functional Dependency is referred to as the determinant?
What is a Full Function Dependency in terms of attributes?
What is a Full Function Dependency in terms of attributes?
In the context of Functional Dependency, what does 'X functionally determines Y' imply?
In the context of Functional Dependency, what does 'X functionally determines Y' imply?
'An attribute is fully functional dependent on another attribute if it is Functionally Dependent on that attribute and not on any of its proper subset.' This statement best describes:
'An attribute is fully functional dependent on another attribute if it is Functionally Dependent on that attribute and not on any of its proper subset.' This statement best describes:
'R: X Y' represents a Functional Dependency where:
'R: X Y' represents a Functional Dependency where:
'Armstrong’s Axioms' are used to infer additional ______ in a database.
'Armstrong’s Axioms' are used to infer additional ______ in a database.
If an attribute Q is functionally dependent on another attribute P, and not on any proper subset of P, what kind of dependency exists between them?
If an attribute Q is functionally dependent on another attribute P, and not on any proper subset of P, what kind of dependency exists between them?
Study Notes
Functional Dependencies
- A functional dependency exists between two attributes X and Y if the values of X uniquely determine the values of Y, denoted as X → Y.
- In the relation Emp_Project, EmpID, ProjectID, and Days are functionally dependent, but not fully functional dependent.
- A subset of attributes {EmpID, ProjectID} can determine the Days spent on the project by an employee.
Types of Functional Dependencies
- Trivial Functional Dependency: a dependent is a subset of the determinant, e.g., {enrolment_no, name} → name.
- Non-Trivial Functional Dependency: a dependent is not a subset of the determinant, e.g., {enrolment_no, name} → result.
Armstrong's Axioms
- A set of rules to derive new functional dependencies from existing ones:
- Reflexivity: if B is a subset of A, then A → B.
- Augmentation: if A → B, then AC → BC.
- Transitivity: if A → B and B → C, then A → C.
- Pseudo-transitivity: if A → B and BD → C, then AD → C.
- Self-determination: A → A.
- Decomposition: if A → BC, then A → B and A → C.
- Union: if A → B and A → C, then A → BC.
- Composition: if A → B and C → D, then A, C → BD.
Decomposition
- The process of breaking down a relation into two or more relations.
- Two types of decomposition:
- Lossy Decomposition: decomposing a relation into two or more relational schemas, resulting in loss of information.
- Lossless Join Decomposition: decomposing a relation into two or more relational schemas, preserving the original information.
Full Functional Dependency
- An attribute is fully functional dependent on another attribute if it is functionally dependent on that attribute and not on any of its proper subset.
- Example: an attribute Q is fully functional dependent on another attribute P, if it is functionally dependent on P and not on any of the proper subset of P.
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Description
Test your understanding of functional dependencies in database management systems with this quiz. Explore how different attributes in a database table are related to each other and determine their dependency levels. Challenge yourself with questions on trivial functional dependency, fully functional dependency, and more.
