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What are the properties of functional dependency?
A functional dependency FD: X → Y is called trivial if Y is a subset of X. In other words, a dependency FD: X → Y means that the values of Y are determined by the values of X. Two tuples sharing the same values of X will necessarily have the same values of Y. where Z = U − XY are the rest of the attributes.
When a functional dependency is present the dependency is specified as a between the attributes?
A functional dependency is a property of the semantics of the attributes in a relation. The semantics indicate how attributes relate to one another, and specify the functional dependencies between attributes. When a functional dependency is present, the dependency is specified as a constraint between the attributes.
What is fully functional dependency?
A full functional dependency is a state of database normalization that equates to the normalization standard of Second Normal Form (2NF). In brief, this means that it meets the requirements of First Normal Form (1NF), and all non-key attributes are fully functionally dependent on the primary key.
What is full functional dependency explain with an example?
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. For 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.
What is a functional dependency in a table?
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.
What is the Armstrong’s axioms property of functional dependency?
Armstrong’s Axioms Property of Functional Dependency Armstrong’s Axioms property was developed by William Armstrong in 1974 to reason about functional dependencies. The property suggests rules that hold true if the following are satisfied:
What is a functional dependency between field X and field Y?
A functional dependency between two columns, X and Y, means that for any two records R1 and R2 in the table, if field X of record R1 contains value x and field X of record R2 contains the same value x, then if field Y of record R1 contains the value y, then field Y of record R2 must contain the value y.
How is deptid and DeptName a functional dependency?
The DeptId is our primary key. Here, DeptId uniquely identifies the DeptName attribute. This is because if you want to know the department name, then at first you need to have the DeptId. Therefore, the above functional dependency between DeptId and DeptName can be determined as DeptId is functionally dependent on DeptName −