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Multivalued dependencies are also referred to as tuple generating dependencies. After the Boyce -Codd normal form the results may be devoid of any functional dependencies but it may encounter multivalued dependencies as the multivalued dependencies also cause redundancy of data.
For eg:
If there are 3 attributes involved in a relation,A,B, and C..
Then for every value of A we will have respective values for B and C.. But it is a necessary in the 4th normal form that both B and C values are independent of each other.
This is represented by .,,
A->>B
A->>C..
MVD or Multivalued Dependency is a dependency where one attribute value is potentially a "multivalued fact" about another and the attributes must be independent of each other.
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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 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 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
What is functional dependency in DBMS?
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.
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.
What is mvd in dbms?
multivalued data
What is multivalued attribute?
Potential to have more than one value for an attribute
A region that belongs to another state?
Dependency
What is an arcsine?
An arcsine is any of the single- or multivalued functions which are inverses of the sine function.
What are some examples of a multivalued attribute?
date of birth determines a person's age.
What is classical logic and multivalued logic?
Classical Logic allows two truth values, True and False. Multivalued or "many-valued logic" allows other kinds of truth values and it allows there to be more than two truth values.
What is trivial dependency?
A DEPENDENCY X->Y IS SAID TO BE TRIVIAL DEPENDENCY IF Y IS A PROPER SUBSET OF X OTHERWISE NON TRIVIAL DEPENDENCY.
Why 4NF is preferable then bcnf .with example?
Normalization is a process to reduce the redundancy by removing function dependencies BCNF (Boyece code normal form) has all functional dependencies A to B are trivial of discriminator should be superkey. To get relation in BCNF, Splitting the relation schema not neccessarily preserve all functional dependency, Loss less decomposition and dependency are main points for the normalization sometime, it is not possible to get a BCNF decomposition that is dependency, preserving. While 4NF has very similar definition as BCNF. A relational Schema is in 4NF, if all multivalued dependencies A to B are trivial and determinate A is superkey of schema. If a relational schema is in 4nf, it is already in BCNF. and 4NF decomposition preserve the all functional dependency. so 4NF is preferable than to have BCNF.
What is post-natal dependency?
Dependency after birth.
What is non trivial dependency?
A DEPENDENCY X->Y IS SAID TO BE TRIVIAL DEPENDENCY IF Y IS A PROPER SUBSET OF X OTHERWISE NON TRIVIAL DEPENDENCY.
What is an arctangent?
An arctangent is any of several single-valued or multivalued functions which are inverses of the tangent function.
What is an arccosine?
An arccosine is any of several single-valued or multivalued functions which are inverses of the cosine function.
