Understanding Functional Dependencies for Database Normalization

Identifying Functional Dependencies in a Table

Write a SQL query to identify functional dependencies in a table.

Solution:

-- Analyze functional dependencies in the Employees table.
SELECT DISTINCT DepartmentID, DepartmentName
FROM Employees;

-- Verify that DepartmentName depends only on DepartmentID.

Explanation:

• Purpose of the Query :
• The goal is to identify functional dependencies to guide normalization efforts.
• Key Components :
• DISTINCT: Ensures that each department name corresponds to a unique department ID.
• Verifies that DepartmentName depends only on DepartmentID.
• Why Identify Functional Dependencies? :
• Functional dependencies reveal how attributes relate to each other, helping to achieve higher normal forms.
• They guide decisions about splitting tables and reducing redundancy.
• Real-World Application :
• In HR systems, identifying dependencies ensures that department details are stored consistently.

Notes:

• Functional dependencies are the foundation of normalization.
• Use them to determine candidate keys and eliminate redundancies.
• Important Considerations:
• Document all dependencies before designing the database schema.

For more Practice: Solve these Related Problems:

• Write a SQL query to identify functional dependencies in a table storing customer orders and shipping addresses.
• Write a SQL query to analyze functional dependencies in a table containing product categories and subcategories.
• Write a SQL query to determine if employee roles depend solely on their department in a given table.
• Write a SQL query to verify functional dependencies between supplier IDs and supplier locations in a procurement table.

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Next SQL Exercise: Designing a Recursive Relationship for Hierarchical Data.