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Functional Dependencies A Functional Dependency describes a relationship between attributes in a single relation. An attribute is functionally dependant on another if we can use the value of one attribute to determine the value of another. Example: Employee_Name is functionally dependant on Social_Security_Number because Social_Security_Number can be used to determine the value of Employee_Name. We use the symbol -> to indicate a functional dependency. -> is read functionally determines Student_ID -> Student_Major Student_ID, Course#, Semester# -> Grade SKU -> Compact_Disk_Title, Artist Model, Options, Tax -> Car_Price Course_Number, Section -> Professor, Classroom, Number of Students The attributes listed on the left hand side of the -> are called determinants. One can read A -> B as, "A determines B".
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What is non trivial functional dependency?
-->non trivial functional dependency is totally opposite to the trivial functional dependency. --> non trivial dependency means X-->Y that is if Y is not proper subset of X table or relation with X then it said to be non trivial functional dependency.
What is functional dependency in oracle?
In Oracle, functional dependency is when the value of one thing is completely determined by another thing. Functional dependency happens when one attribute determines another attribute in a relation.
Difference between partial dependency and fully functional dependency?
The difference is that partial dependency is when a database's attribute is only partially dependent on the primary key. Fully functional dependency is when the attribute is entirely dependent on the key.
What is Trivial and Non Trivial Dependency?
Trivial functional dependencyA trivial functional dependency is a functional dependency of an attribute on a superset of itself. {Employee ID, Employee Address} → {Employee Address} is trivial, as is {Employee Address} → {Employee Address}.
What is Transitive functional dependency?
A functional dependency X->Y is transitive in R, if there exists an attribute Z in R, such that X-> Z, Z-> Y .
What is difference between Partial Functional Dependency and Full Functional Dependency?
A functional dependency is defined as a constraint between two sets of attributes in a relation from a database.Given a relation R, a set of attributes X in R is said to functionally determine another attribute Y, also in R, (written X→ Y) if and only if eachX value is associated with at most oneY value.A functional dependency X --> Y is full functional dependency if removal of any attribute 'k' from X means that the dependency does not hold any more. Full functional dependency is minimal in size.Partial Functional Dependency Indicates that if A and B are attributes of a table, B is partially dependent on A if there is some attribute that can be removed from A and yet the dependency still holds.A key is a set of attributes that uniquely identifies an entire tuple, a function dependency allow us to express constraints that uniquely identify the values of certain attribute.
Fully functional dependency?
A functional dependency X --> Y is full functional dependency if removal of any attribute 'k' from X means that the dependency does not hold any more.Full functional dependency is minimal in size (contain non-redundant data)In a relation R , attribute B of R is fully functionallydependent on an attribute or set of attributes A of R , if B is functionally dependent on A, but not functionally dependent on any proper subset of A.ORAàB is a fully functionally dependency, if removal of any attribute X from A would result into the cancellation of dependency. i.e. (A-{X})-->B does not hold.
What is Partial functional dependency?
Partial Functional Dependency Indicates that if A and B are attributes of a table , B is partially dependent on A if there is some attribute that can be removed from A and yet the dependency still holds. Say for Ex, consider the following functional dependency that exists in the Tbl_Staff table: StaffID,Name -------> BranchID BranchID is functionally dependent on a subset of A (StaffID,Name), namely StaffID. Source :http://www.mahipalreddy.com/dbdesign/dbqa.htm
How functional dependency is related to database table design?
The functional dependency is related to the database table design through the foreign and primary keys. The foreign and primary keys are functionally dependent on each other.
How many types of functional dependencies in DBMS?
In DBMS there is three type of functional dependency1 FULL FUNCTION DEPENDENCY.2 PARTIALLY FUNCTION DEPENDENCY.3 TRACIENT FUNCTION DEPENDENCY.Functional Dependency can be classified as follows:Full Functional dependency Indicates that if A and B are attributes(columns)of a table, B is fully functionally dependent on A if B is functionally dependent on A ,but not on any proper subset of A.Partial Functional Dependency Indicates that if Aand B are attributes of a table , B is partially dependent on A if there is some attribute that can be removed from A and yet the dependency still holds.Transitive Functional Dependency: A condition where A , B and C are attributes of a table such that if A is functionally dependent on B and Bis functionally dependent on C then C is Transitively dependent on A via BFor Detailed explanation with example visit Authors original Postinghttp://www.mahipalreddy.com/dbdesign/dbqa.htm
Find out functional dependencies?
A constraint between two sets of attributes is known as functional dependency in relational database. Determination of functional dependencies is vital in database denormalization, normalization and relational model.
Describe the dependency diagram and explain its purpose?
A dependency diagram is a visual representation of a dependency graph. Dependency diagrams are integral to software development, outlining the complex, interrelationships of various functional elements. Typically in a dependency diagram, arrows point from each module to other modules which they are dependent upon.The dependency diagram is used as an aid to normalization within database design.
