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Questions and Answers
Which term is used to denote a functional dependency from X to Y?
In the relation Account(ano, balance, bname), which attribute fully functionally depends on 'ano'?
What does FD stand for in the context of Functional Dependency?
Which side of a Functional Dependency is referred to as the determinant?
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What is a Full Function Dependency in terms of attributes?
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In the context of Functional Dependency, what does 'X functionally determines Y' imply?
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'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:
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'R: X Y' represents a Functional Dependency where:
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'Armstrong’s Axioms' are used to infer additional ______ in a database.
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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?
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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.
