CONCEPT OF FUNCTIONAL DEPENDENCY IN DBMS :
Functional dependency is a relationship that exists between two attributes.
In other words , functional dependency is a method which describes the relationship between the attributes. I f x->y then it means x determines y or y is determined by x . Here x is determinant attribute and y is dependent attribute.
For example : If S_ID -> S_NAME so we can say that S_NAME is functionally dependent on S_ID.
TYPES OF DEPENDENCY :
There are two types of functional dependency : -
1. Trivial functional dependency
2. Non trivial functional dependency
1. Trivial functional dependency :
Functional dependency is a relationship that exists between two attributes.
In other words , functional dependency is a method which describes the relationship between the attributes. I f x->y then it means x determines y or y is determined by x . Here x is determinant attribute and y is dependent attribute.
For example : If S_ID -> S_NAME so we can say that S_NAME is functionally dependent on S_ID.
TYPES OF DEPENDENCY :
There are two types of functional dependency : -
1. Trivial functional dependency
2. Non trivial functional dependency
1. Trivial functional dependency :
- It says if x -> y then y is the subset of x.
- In other words, if x -> y then intersection of x and y could not be empty . For example , If we take S_ID S_NAME intersection S_ ID = S_ID.
- It says if x -> y then y is not a subset of x .
- In other words, if x -> y then intersection of x and y will be null . For example , If we take S_ID intersection S_ NAME = NULL.