How do you find the closure of a functional dependency set?

Determine each set of attributes X that appears as a left hand side of some FD in F. Determine the set X+ of all attributes that are dependent on X, as given in above example. In other words, X+ represents a set of attributes that are functionally determined by X based on F. And, X+ is called the Closure of X under F.

How do you find functional dependencies in a relation?

Functional Dependencies in a relation are dependent on the domain of the relation. Consider the STUDENT relation given in Table 1. We know that STUD_NO is unique for each student. So STUD_NO->STUD_NAME, STUD_NO->STUD_PHONE, STUD_NO->STUD_STATE, STUD_NO->STUD_COUNTRY and STUD_NO -> STUD_AGE all will be true.

What is closure set of dependencies and of attributes?

The closure of a set of attributes X is the set of those attributes that can be functionally determined from X. The closure of X is denoted as X+. When given a closure problem, you’ll have a set of functional dependencies over which to compute the closure and the set X for which to find the closure.

How do you calculate F closure?

The closure of F, denoted as F+, is the set of all regular FDs that can be derived from F. Do not confuse the closure of F with the closure of an attribute set. Example. Assume that there are 4 attributes A, B, C, D, and that F = {A → B, B → C}.

Which is an example of a functional dependency set?

Functional Dependency Set: Functional Dependency set or FD set of a relation is the set of all FDs present in the relation. For Example, FD set for relation STUDENT shown in table 1 is: Attribute Closure: Attribute closure of an attribute set can be defined as set of attributes which can be functionally determined from it.

How to calculate closure of a functional dependency?

There are three steps to calculate closure of functional dependency. These are: Step-1 : Add the attributes which are present on Left Hand Side in the original functional dependency. Step-2 : Now, add the attributes present on the Right Hand Side of the functional dependency.

How to find attribute closure in a relation?

Non-Trivial functional dependency may or may not hold in a relation. e.g; E-ID->E-NAME is a non-trivial functional dependency which holds in the above relation. Let X , Y, and Z are sets of attributes in a relation R. There are several properties of functional dependencies which always hold in R also known as Armstrong Axioms.

What are the properties of functional dependencies in R?

There are several properties of functional dependencies which always hold in R also known as Armstrong Axioms. Reflexivity: If Y is a subset of X, then X → Y. e.g.; Let X represents {E-ID, E-NAME} and Y represents {E-ID}. {E-ID, E-NAME}->E-ID is true for the relation. Augmentation: If X → Y, then XZ → YZ. e.g.;