This set of Oracle Database Multiple Choice Questions & Answers (MCQs) focuses on “Normalization”.
1. A table is in BCNF if it is in 3NF and if every determinant is a ___________ key.
a) Dependent
b) Normal
c) Candidate
d) Both Normal and Candidate
View Answer
Explanation: A table is in Boyce-Codd normal form (BCNF) if and only if it is in 3NF and every determinant is a candidate key.
2. The ___________ normalization introduced by Chris Date, Hugh Darwen, and Nikos Lorentzos.
a) Third
b) Fourth
c) Fifth
d) Sixth
View Answer
Explanation: Chris Date, Hugh Darwen, and Nikos Lorentzos introduced Sixth Normal form (6NF).
3. A table is in 3NF if it is in 2NF and if it has no ____________
a) Functional Dependencies
b) Transitive Dependencies
c) Trivial Functional Dependency
d) Multivalued Dependencies
View Answer
Explanation: For a relation to be in Third Normal Form, it must be in Second Normal form and the following must satisfy:No non-prime attribute is transitively dependent on prime key attribute For any non-trivial functional dependency, X -> A, then eitherX is a superkey or,A is prime attribute.
4. Every constraint on the table is a logical consequence of the table’s
a) Fourth normal form
b) Fifth normal form
c) Domain/key normal form
d) None of the Mentioned
View Answer
Explanation: A relation is in domain-key normal form (DK/NF) if every constraint on the relation is a logical consequence of the definition of keys and domains.
5. A ___________ is an indirect functional dependency, one in which X->Z only by virtue of X->Y and Y->Z.
a) Multivalued Dependencies
b) Join Dependency
c) Trivial Functional Dependency
d) Transitive Dependencies
View Answer
Explanation: Third Normal Form deals with something called ‘transitive’ dependencies. This means if we have a primary key A and a non-key domain B and C where C is more dependent on B than A and B is directly dependent on A, then C can be considered transitively dependent on A.
6. In a given relationship R, if an attribute A uniquely defines all other attributes, then the attribute A is a key attribute which is also known as the _________ key.
a) Candidate
b) Join
c) Functional
d) None of the Mentioned
View Answer
Explanation: A candidate key is a column, or set of columns, in a table that can uniquely identify any database record without referring to any other data. Each table may have one or more candidate keys.
7. Anomalies are avoided by splitting the offending relation into multiple relations, is also known as
a) Accupressure
b) Decomposition
c) Precomposition
d) Both Decomposition and Precomposition
View Answer
Explanation: Eliminate redundancy by decomposing a relation into several relations in a higher normal form.
8. Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
a) A -> B
b) A -> C
c) A -> (B,C)
d) (B,C) -> A
View Answer
Explanation: Transitivity rule: Same as transitive rule in algebra, if a -> b holds and b -> c holds then a -> c also hold. a -> b is called as a functionally determines b.
9. When the values in one or more attributes being used as a foreign key must exist in another set of one or more attributes in another table, we have created a(n):
a) Transitive Dependency
b) Insertion Anomaly
c) Referential Integrity Constraint
d) Normal Form
View Answer
Explanation: Referential Integrity is set of constraints applied to foreign key which prevents entering a row in child table for which you don’t have any corresponding row in parent table i.e. entering NULL or invalid foreign keys.
10. Which of the following is not a restriction for a table to be a relation?
a) The cells of the table must contain a single value
b) All of the entries in any column must be of the same kind
c) The columns must be ordered
d) No two rows in a table may be identical
View Answer
Explanation: To format the columns differently, assign a unique alias to each column within the SELECT command itself (do not use the ALIAS clause of the COLUMN command) and enter a COLUMN command for each column’s alias.
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