How do you know if an attribute is extraneous?
Step 1: Find ({α} – A)+ using the dependencies of F. Step 2: If ({α} – A)+ contains all the attributes of β, then A is extraneous. Case 2 (RHS): To find if an attribute A in β is extraneous or not. That is, to test if an attribute of Right Hand Side of a functional dependency is Extraneous or not.
How an extraneous attribute A can be identified for the functional dependency α β in F?
Attribute A is extraneous in α if A ∈ α, and F logically implies (F −{α → β}) ∪{(α − A) → β}. Attribute A is extraneous in β if A ∈ β, and the set of functional dependencies (F − {α → β}) ∪{α → (β − A)} logically implies F.
What is meant by canonical cover?
In DBMS, A canonical 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.
What is irreducible or canonical form?
In case of a violation of functional dependencies in the new database state, the rollback of the system must take place. A canonical cover or irreducible a set of functional dependencies FD is a simplified set of FD that has a similar closure as the original set FD.
What are extraneous attributes?
Extraneous attributes: An attribute of a functional dependency is said to be extraneous if we can remove it without changing the closure of the set of functional dependencies.
What is non prime attribute in database?
Non-prime attribute − An attribute, which is not a part of the prime-key, is said to be a non- prime attribute. If we follow second normal form, then every non-prime attribute should be fully functionally dependent on prime key attribute.
Can we infer NP → LM from F?
[2pt] Can we infer NP → LM from F? Yes,because NP→NPOLM, so,NP→LM[3pt] Can we infer NQ → LO from F?
What is extraneous attribute?
What is the difference between canonical cover and minimal cover?
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 redundant functional dependency?
A functional dependency in the set is redundant if it can be derived from the other functional dependencies in the set.
What is FC in DBMS?
DBMSDatabaseBig Data Analytics. Canonical cover is called minimal cover which is called the minimum set of FDs. A set of FD FC is called canonical cover of F if each FD in FC is a Simple FD, Left reduced FD and Non-redundant FD. Simple FD − X->Y is a simple FD if Y is a single attribute.
What is a prime and non prime attribute?
Prime attribute − An attribute, which is a part of the prime-key, is known as a prime attribute. Non-prime attribute − An attribute, which is not a part of the prime-key, is said to be a non- prime attribute.
What are non key attributes?
A non key attribute in sql server is a columns which can not be used to identify a record uniquely for example name or age columns in customer table.
What is prime attribute and non-prime attribute?
What is multivalued dependency in DBMS?
The concept of MVD or Multivalued dependency refers to having multiple rows in a given table. Thus, it implies that there is a presence of multiple other rows in the very same table. Thus, a multivalued dependency would prevent the 4NF.
What is non-prime attribute in database?
What is closure of attribute in DBMS?
DBMSDatabaseBig Data Analytics. Closure of an attribute x is the set of all attributes that are functional dependencies on X with respect to F. It is denoted by X+ which means what X can determine.
What is non trivial functional dependency?
Non-trivial Functional Dependency In Non-trivial functional dependency, the dependent is strictly not a subset of the determinant. i.e. If X → Y and Y is not a subset of X, then it is called Non-trivial functional dependency.
What is key and non key attribute?
Key Attribute & Non-key Attribute As the name suggests key attribute will uniquely identify the entities whereas the non-key attributes would not be able to uniquely identify the entities. Key Attribute. A key attribute is used to uniquely identify the entities of an entity type.
Is non key attribute and non-prime attribute same?
Non-prime attribute means the same as non-key attribute.
What does extraneous mean?
Extraneous variables, also known as confounding variables, are defined as all other variables that could affect the findings of an experiment but are not independent variables. For example, in research about the impact of sleep deprivation on test performance, the researcher will divide the participants into two groups.
What are extraneous variables in research?
Extraneous variables are all variables, which are not the independent variable, but could affect the results of the experiment. The researcher wants to make sure that it is the manipulation of the independent variable that has an effect on the dependent variable.
How to test if an attribute is extraneous or not?
Case 1 (LHS): To find if an attribute A in α is extraneous or not. That is, to test if an attribute of Left Hand Side of a functional dependency is Extraneous or not. Step 2: If ( {α} – A)+ contains all the attributes of β, then A is extraneous.
What is the difference between confounding and controlling extraneous variables?
Controlling extraneous variables is an important aspect of experimental design. When you control an extraneous variable, you turn it into a control variable. A confounding variable is a type of extraneous variable that is associated with both the independent and dependent variables.