Database Management System Questions and Answers

Q: The part of a database management system which ensures that the data remains in a consistent state is

Correct answer: transaction managerThe transaction manager ensures that every transaction takes the database from one consistent state to another, committing all of its changes or none of them. The buffer and file managers move pages, and the integrity manager checks constraints on individual operations.

Q: ______defines the structure of a relation which consists of a fixed set of attribute-domain pairs.

Correct answer: SchemaA schema is the description of a relation's structure: its attributes and the domain of each. An instance is the set of tuples present at a given moment, which changes while the schema stays fixed.

Q: Which normal form is considered adequate for normal relational database design?

Correct answer: 3NFThird normal form removes both partial and transitive dependencies and can always be reached without losing any functional dependency, which is why it is the normal form ordinarily aimed at. BCNF is stronger but may not be dependency preserving, and 4NF and 5NF address problems that arise less often.

Q: Which of the syntax is correct for insert statement? i) insert into values ii) insert into (column list) values

Correct answer: Both of themBoth forms are valid. Naming the columns explicitly is safer, because the statement then does not depend on the order in which the columns were defined; omitting the list requires a value for every column in table order.

Q: The fact that all employees of a particular organization should not have salaries more than $10000 is a _____ constraint.

Correct answer: DomainA limit on the values a single attribute may take is a domain constraint - here, that salary must not exceed $10000. A tuple constraint would relate two attributes of the same row, and a schema constraint the structure itself.

Q: Which of the following is not a logical database structure?

Correct answer: ChainThe three logical database structures are hierarchical (tree), network and relational. A chain is a way of linking records physically, not a logical model of the data.

Q: Tree structures are used to store data in

Correct answer: Hierarchical model.The hierarchical model arranges records in a tree, each child having exactly one parent. The network model uses a graph, which allows several parents, and the relational model uses tables with no structural links at all.

Q: The rule that a value of a foreign key must appear as a value of some specific table is called a

Correct answer: Referential constraint.A referential integrity constraint requires every value of a foreign key to appear as a key value in the referenced table, so no reference points at a row that does not exist. Integrity constraint is the general category, of which this is one kind.

Q: Which of the following relational algebraic operations is not from set theory?

Correct answer: SelectUnion, intersection and Cartesian product are all operations of set theory, applied here to relations. Selection is peculiar to relational algebra: it picks the tuples that satisfy a predicate, which set theory has no notion of.

Q: Consider the join of relation R with a relation S. If R has m tuples and S has n tuples, then the maximum and minimum size of the join respectively are

Correct answer: mn and 0A join is a subset of the Cartesian product, so at most every pair of rows matches, giving $ m \times n $ tuples; and at fewest no pair matches, giving 0. The extremes are the product and the empty relation.

51.

The part of a database management system which ensures that the data remains in a consistent state is

A.authorization and integrity manager
B.buffer manager
C.transaction manager
D.file manager

Answer: C

Correct answer: transaction manager

The transaction manager ensures that every transaction takes the database from one consistent state to another, committing all of its changes or none of them. The buffer and file managers move pages, and the integrity manager checks constraints on individual operations.

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52.

______defines the structure of a relation which consists of a fixed set of attribute-domain pairs.

A.Instance
B.Program
C.Schema
D.Super Key

Answer: C

Correct answer: Schema

A schema is the description of a relation's structure: its attributes and the domain of each. An instance is the set of tuples present at a given moment, which changes while the schema stays fixed.

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53.

Which normal form is considered adequate for normal relational database design?

A.2NF
B.5NF
C.4NF
D.3NF

Answer: D

Correct answer: 3NF

Third normal form removes both partial and transitive dependencies and can always be reached without losing any functional dependency, which is why it is the normal form ordinarily aimed at. BCNF is stronger but may not be dependency preserving, and 4NF and 5NF address problems that arise less often.

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54.

Which of the syntax is correct for insert statement?
i) insert into values
ii) insert into (column list) values

A.i-only
B.ii-only
C.Both of them
D.None of them

Answer: C

Correct answer: Both of them

Both forms are valid. Naming the columns explicitly is safer, because the statement then does not depend on the order in which the columns were defined; omitting the list requires a value for every column in table order.

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55.

The fact that all employees of a particular organization should not have salaries more than $10000 is a _____ constraint.

A.Schema
B.Tuple
C.Domain
D.Relational

Answer: C

Correct answer: Domain

A limit on the values a single attribute may take is a domain constraint - here, that salary must not exceed $10000. A tuple constraint would relate two attributes of the same row, and a schema constraint the structure itself.

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56.

Which of the following is not a logical database structure?

A.Chain
B.Network
C.Tree
D.Relational

Answer: A

Correct answer: Chain

The three logical database structures are hierarchical (tree), network and relational. A chain is a way of linking records physically, not a logical model of the data.

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57.

Tree structures are used to store data in

A.Network model.
B.Relational model.
C.Hierarchical model.
D.File based system.

Answer: C

Correct answer: Hierarchical model.

The hierarchical model arranges records in a tree, each child having exactly one parent. The network model uses a graph, which allows several parents, and the relational model uses tables with no structural links at all.

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58.

The rule that a value of a foreign key must appear as a value of some specific table is called a

A.Referential constraint.
B.Index.
C.Integrity constraint.
D.Functional dependency.

Answer: A

Correct answer: Referential constraint.

A referential integrity constraint requires every value of a foreign key to appear as a key value in the referenced table, so no reference points at a row that does not exist. Integrity constraint is the general category, of which this is one kind.

Discuss in Forum

59.

Which of the following relational algebraic operations is not from set theory?

A.Union
B.Intersection
C.Cartesian Product
D.Select

Answer: D

Correct answer: Select

Union, intersection and Cartesian product are all operations of set theory, applied here to relations. Selection is peculiar to relational algebra: it picks the tuples that satisfy a predicate, which set theory has no notion of.

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60.

Consider the join of relation R with a relation S. If R has m tuples and S has n tuples, then the maximum and minimum size of the join respectively are

A.m+n and 0
B.m+n and |m-n|
C.mn and 0
D.mn and m+n

Answer: C

Correct answer: mn and 0

A join is a subset of the Cartesian product, so at most every pair of rows matches, giving $ m \times n $ tuples; and at fewest no pair matches, giving 0. The extremes are the product and the empty relation.

Discuss in Forum

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