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How do you find the minimal set of functional dependencies?

How do you find the minimal set of functional dependencies?

Here, EI → C is redundant (C can be determined using other FD, in this case, A → C). Hence, the minimal cover Fc = {A → C, C → D, C → I, EC → A, EC → B}. Hence, set of functional dependencies Fc is the minimal cover for the set F.

What is a minimal basis?

Given a set F of FDs, a minimal basis is a set G of FDs for which: Every FD in G has just one attribute on its right side. G is a basis for F . Removing any FD from G results in a set of FDs that is not a basis for F .

What is a functional dependency in database?

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.

How do you calculate minimal basis in DBMS?

Minimal Cover

  1. Steps to Find Minimal Cover.
  2. 1) Split the right-hand attributes of all FDs. Example.
  3. 2) Remove all redundant FDs. Example.
  4. 3) Find the Extraneous attribute and remove it. Example.
  5. Example 1.
  6. Step 1: {A->C, AC->D, E->H, E->A, E->D}
  7. Step 2: {A->C, AC->D, E->H, E->A}
  8. Step 3: {AC->D}

Is Canonical and minimal cover the same?

A canonical cover is “allowed” to have more than one attribute on the right hand side. A minimal cover cannot. As an example, the canonical cover may be “A -> BC” where the minimal cover would be “A -> B, A -> C”. That is the only difference.

What is minimal cover DBMS?

A minimal cover is a simplified and reduced version of the given set of functional dependencies. Since it is a reduced version, it is also called as Irreducible set. It is also called as Canonical Cover. Steps to Find Minimal Cover.

What are the types of functional dependency?

Types of Functional dependencies in DBMS:

  • Trivial functional dependency.
  • Non-Trivial functional dependency.
  • Multivalued functional dependency.
  • Transitive functional dependency.

What is functional dependency and types?

Functional Dependency is when one attribute determines another attribute in a DBMS system. Axiom, Decomposition, Dependent, Determinant, Union are key terms for functional dependency. Four types of functional dependency are 1) Multivalued 2) Trivial 3) Non-trivial 4) Transitive.

What is partial dependency in DBMS?

Partial dependency occurs when one primary key determines some other attribute/attributes. On the other hand, transitive dependency occurs when some non-key attribute determines some other attribute.

Is minimal cover unique?

Minimal covers are not unique: for 3NF design we use a particular kind of minimal cover, called a canonical cover. Canonical covers are computed as follows: Decompose fds into non-trivial fds that have only one attribute at the right side.

What is minimal cover and canonical cover in DBMS?

What is functional dependency in DBMS?

What is Functional Dependency. Functional dependency in DBMS, as the name suggests is a relationship between attributes of a table dependent on each other. Introduced by E. F. Codd, it helps in preventing data redundancy and gets to know about bad designs. To understand the concept thoroughly, let us consider P is a relation with attributes A

How to make functional dependency easier to understand?

Above suggests the following: The following is an example that would make it easier to understand functional dependency − We have a table with two attributes − DeptId and DeptName. The DeptId is our primary key. Here, DeptId uniquely identifies the DeptName attribute.

What is minimal cover of functional dependencies?

There can be many such minimal covers for a set of functional dependencies F. A set of FDs F is minimum if F has as few FDs as any equivalent set of FDs. [ How to find minimal cover? – Refer here]. 1. Right Hand Side (RHS) of all FDs should be single attribute. 2. Remove extraneous attributes. [ What is extraneous attribute? Refer here]. 3.

What is the functional dependency between deptid and DeptName?

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 −