Mastering Functional Dependencies in Database Design

Understanding Functional Dependencies in Database Design

• A functional dependency (FD) is a relationship between two attributes, typically between the PK and other non-key attributes within a table.
• For any relation R, attribute Y is functionally dependent on attribute X (usually the PK), if for every valid instance of X, that value of X uniquely determines the value of Y.
• The left side of the FD diagram is called the determinant, and the right side is the dependent.
• Armstrong’s axioms are a set of inference rules used to infer all the functional dependencies on a relational database.
• The axiom of reflexivity says, if Y is a subset of X, then X determines Y.
• The axiom of augmentation says if X determines Y, then XZ determines YZ for any Z.
• The axiom of transitivity says if X determines Y, and Y determines Z, then X must also determine Z.
• The union rule suggests that if two tables are separate, and the PK is the same, you may want to consider putting them together.
• Decomposition is the reverse of the union rule.
• A dependency diagram illustrates the various dependencies that might exist in a non-normalized table.
• Actual data can help clarify which attributes are dependent and which are determinants.
• Inference rules can be used to identify and fix problems with partial dependencies, transitive dependencies, and other issues that arise in database design.

Test your knowledge on functional dependencies in database design with this informative quiz. Learn about the relationship between attributes, Armstrong's axioms, and the union rule. Explore the process of decomposition and how to use inference rules to identify and fix issues with partial and transitive dependencies. Whether you're a beginner or an expert in database design, this quiz is a great way to enhance your skills and understanding of functional dependencies.