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What is Functional Dependency?
Functional dependency is a fundamental concept in the field of databases, especially in the context of relational databases. It refers to a relationship between two sets of attributes within a relation (table) in a database. More specifically, it describes how the values of one set of attributes determine the values of another set of attributes.
In simpler terms, if we have two attributes A and B in a relation, we say that B is functionally dependent on A if, for every given value of A, there is a unique value of B associated with it. This relationship can be represented as A -> B, read as “A determines B” or “B is functionally dependent on A.”
Functional dependencies play a crucial role in database design and normalization. They help ensure the integrity and consistency of data by eliminating redundant information. By identifying and understanding the functional dependencies within a database, we can optimize its structure and reduce data storage requirements.
Data Dependencies in Relational Databases
Now, let’s delve deeper into the types of functional dependencies that can exist in a relational database:
1. Full Functional Dependency: A functional dependency A -> B is called a full functional dependency if and only if B is not functionally dependent on any proper subset of A. In other words, every attribute in A is necessary for determining B, and removing any attribute from A would break the dependency.
2. Partial Functional Dependency: A functional dependency A -> B is considered a partial functional dependency if B is functionally dependent on only a part of A. This means that removing some attributes from A would not break the dependency.
3. Transitive Dependency: A functional dependency A -> B and B -> C together imply a transitive dependency A -> C, even if A and C are not directly dependent on each other. This type of dependency is important for understanding the relationships between multiple attributes in a database.
Understanding and identifying these data dependencies is crucial for proper database design and implementation. By correctly analyzing the functional dependencies present in a database, we can ensure efficient and meaningful data storage, retrieval, and modification operations.
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