Functional Dependency: Simplified Overview

Introduction

• Functional Dependency: A core concept in database design, particularly relevant to keys and normalization.
• Similarity to mathematical functions but distinct in meaning.

Mathematical Analogy

• Traditional function: Using input a with function f gives output b (e.g., square function).
• Functional Dependency in databases: Knowing the value of a allows us to determine b from a table.

Key Concepts

• Determinant: Attribute used to determine another attribute.
• Dependent: Attribute that is determined.
• Functional Dependency Definition: A constraint specifying the relationship of one attribute to another in a table.

Examples and Validity

Example 1: Unique Determinant

• Functional Dependency: Roll number determines student name, department name, and department building.
• Validity: Valid, as roll number uniquely identifies the other attributes.

Example 2: Redundant Determinants

• Functional Dependency: Department name determines department building.
• Case: Redundant values in department name.
• Validity: Valid, as identical determinants point to the same dependents.

Example 3: Different Determinants, Same Dependents

• Functional Dependency: Department EC and department ME both determine department building B2.
• Validity: Valid, as multiple determinants can have the same dependent value.

Example 4: Invalid Dependency

• Functional Dependency: Student name determines department name.
• Case: Student names are not unique and point to different departments.
• Validity: Invalid, as identical determinants lead to different dependents.

Summary of Validity Conditions

• Valid:
  • Unique determinant with unique dependent.
  • Identical determinants with identical dependents.
  • Different determinants with the same dependent.
• Invalid:
  • Identical determinants with different dependents.

Conclusion

• Understanding these conditions helps validate functional dependencies.
• Future videos to explore types of dependencies and normal forms.

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• Next Steps: Continue learning about types of functional dependencies and normal forms.