Database Management System Questions and Answers

Q: What are the desirable properties of a decomposition

Correct answer: Dependency preservation.A decomposition should be lossless - the original relation must be recoverable by joining the pieces - and dependency preserving, so that every functional dependency can still be enforced on a single one of the resulting relations. Redundancy is what decomposition removes, not a property it should have.

Q: ______is a preferred method for enforcing data integrity

Correct answer: ConstraintsConstraints are declared as part of the table definition, so the DBMS itself enforces them on every operation and no path can bypass them. A trigger can enforce a rule too, but it is code that has to be written correctly and runs after the fact.

Q: DFD stands for

Correct answer: Data Flow DiagramA data flow diagram shows the processes of a system, the data stores they read and write, and the flows between them - a functional picture, as against the entity-relationship diagram's picture of the data itself.

Q: Which of the following relational algebra operations do not require the participating tables to be union-compatible?

Correct answer: JoinUnion, intersection and difference are set operations, so both operands must have the same number of attributes drawn from the same domains - that is what union-compatible means. A join combines attributes from two different relations and so has no such requirement.

161.

What are the desirable properties of a decomposition

A.Partition constraint.
B.Dependency preservation.
C.Redundancy.
D.Security.

Answer: B

Correct answer: Dependency preservation.

A decomposition should be lossless - the original relation must be recoverable by joining the pieces - and dependency preserving, so that every functional dependency can still be enforced on a single one of the resulting relations. Redundancy is what decomposition removes, not a property it should have.

Discuss in Forum

162.

______is a preferred method for enforcing data integrity

A.Constraints
B.Triggers
C.Stored procedure
D.Cursors

Answer: A

Correct answer: Constraints

Constraints are declared as part of the table definition, so the DBMS itself enforces them on every operation and no path can bypass them. A trigger can enforce a rule too, but it is code that has to be written correctly and runs after the fact.

Discuss in Forum

163.

DFD stands for

A.Data Flow Document
B.Data File Diagram
C.Data Flow Diagram
D.None of the above

Answer: C

Correct answer: Data Flow Diagram

A data flow diagram shows the processes of a system, the data stores they read and write, and the flows between them - a functional picture, as against the entity-relationship diagram's picture of the data itself.

Discuss in Forum

164.

Which of the following relational algebra operations do not require the participating tables to be union-compatible?

A.Union
B.Intersection
C.Difference
D.Join

Answer: D

Correct answer: Join

Union, intersection and difference are set operations, so both operands must have the same number of attributes drawn from the same domains - that is what union-compatible means. A join combines attributes from two different relations and so has no such requirement.

Discuss in Forum

Loading…

Topics

Other Subjects

Tags: Database Management System Questions and Answers || Database Management System MCQ Questions and Answers || Database Management System GK Questions and Answers || Database Management System GK MCQ Questions || Database Management System Multiple Choice Questions and Answers || Database Management System GK || GK on Database Management System || Computer Awareness Questions and Answers || Computer Awareness MCQ Questions and Answers || Computer Awareness GK Questions and Answers || GK on Computer Awareness

Database Management System Questions and Answers

Topics

Other Subjects

About Us

Stay informed about all important Dates & Notifications