Functional dependency in dbms and it's types
In database design, a functional dependency is a relationship between two attributes in a relation (table). It is defined as follows:
Let R be a relation and let A and B be attributes of R. We say that A functionally determines B, denoted A -> B, if and only if, for any two tuples (rows) t1 and t2 in R, if t1 and t2 have the same value for A, then they must have the same value for B.
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| Functional dependency in dbms SKILLS ARENA |
In other words, the value of attribute B is determined by the value of attribute A. For example, consider a table "Employee" with attributes "Employee ID" and "Employee Name". If we know the value of "Employee ID" for an employee, then we can determine the value of "Employee Name" for that employee. Therefore, "Employee ID" -> "Employee Name".
Types of functional dependency in dbms
There are three types of functional dependencies:
Trivial functional dependence:
A functional dependency is trivial if B is a subset of A. For example, if A = {ID, Name} and B = {ID}, then A -> B is a trivial functional dependency.
Non-trivial functional dependency:
A functional dependency is non-trivial if B is not a subset of A. For example, if A = {ID} and B = {Name}, then A -> B is a non-trivial functional dependency.
Full functional dependency:
A functional dependency is full if A determines B, but B does not determine A. In other words, if A -> B and B -> A, then the functional dependency is full. For example, if A = {ID, Name} and B = {ID, Name}, then A -> B is a full functional dependency.
Functional dependencies are an important concept in database design because they help to ensure the integrity and consistency of the data in a database. They can be used to identify and eliminate redundant data, and to ensure that all data in the database is accurately represented.
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Created by-- HARSH CHAUHAN
