Databases MCQs – Set 26

By Atul Sahu • Computer Science, Databases

Databases MCQs – Set 26

UGC NET Paper 2 Computer Science DEC 2012 – Databases

501. Query distinct posting pairs with same skill and p1

Databases • SQL Queries • UGC NET Paper 2 Computer Science DEC 2012

A. 1 B. 3 C. 2 D. 0
Answer: B . SELECT p1.postingNo, p2.postingNo …
Explanation: Self-join with WHERE p1.skill=p2.skill AND p1.postingNo

502. (Duplicate of Q791) Query posting pairs; which SQL?

Databases • SQL Queries • UGC NET Paper 2 Computer Science DEC 2012

A. OR B. NOR C. XOR D. NAND
Answer: B . SELECT p1.postingNo, p2.postingNo …
Explanation: Same self-join solution as Q791.

503. Which abstraction level describes how data are stored?

Databases • DBMS Architecture: Schemas • UGC NET Paper 2 Computer Science DEC 2012

A. physical B. view C. logical D. conceptual
Answer: A. physical
Explanation: The physical schema defines data storage structures and access methods.

504. Referential integrity refers to:

Databases • DBMS Integrity Constraints • UGC NET Paper 2 Computer Science DEC 2012

A. relation key B. foreign key C. primary key D. candidate key
Answer: B. foreign key
Explanation: Ensures that references between tables via foreign keys remain valid.

505. Third normal form is based on:

Databases • Normalization: 3NF • UGC NET Paper 2 Computer Science DEC 2012

A. closure B. transitive dependency C. normal dependency D. functional dependency
Answer: B. transitive dependency
Explanation: 3NF prohibits non-key attributes depending transitively on keys.

506. For a lossless decomposition R→R₁,R₂, R₁∩R₂→R₁ or R₂ must hold.

Databases • Normalization: Lossless Decomposition • UGC NET Paper 2 Computer Science DEC 2012

A. true B. false C. — D. —
Answer: A. true
Explanation: Lossless condition requires intersection’s attributes functionally determine one of the projections.

507. Concurrent updates prevented by __ in multiuser DB

Databases • Concurrency Control • UGC NET Paper 2 Computer Science DEC 2012

A. Jamming B. Password C. Documentation D. Record lock
Answer: D . Record lock
Explanation: Record locking serializes updates to the same record.

508. (Duplicate) Deleting records but keeping structure = PACK.

Databases • DML Commands • UGC NET Paper 2 Computer Science DEC 2012

A. ERASE B. DELETE C. ZAP D. PACK
Answer: D . PACK
Explanation: See Q1032.

509. Fastest among these copy commands is __.

Databases • File Utilities • UGC NET Paper 2 Computer Science DEC 2012

A. COPY TO B. COPY STRUCTURE TO C. COPY FILE D. COPY TO MFILE-DAT DELIMITED
Answer: B . COPY STRUCTURE TO
Explanation: Copies file metadata only, so is fastest.

510. Match OLAP, OLTP, Decision Tree, Neural Network to (DataWarehouse, RDBMS, Classification, Regression):

Databases • Data Analytics • UGC NET Paper 2 Computer Science DEC 2012

A. (b,c,a,d) B. (b,c,d,a) C. (c,b,a,d) D. (c,b,d,a)
Answer: B. (b,c,d,a)
Explanation: OLAP→DataWarehouse (b), OLTP→RDBMS (c), Decision Tree→Classification (d), NN→Regression (a).

511. Data warehousing provides:

Databases • Data Warehousing • UGC NET Paper 2 Computer Science DEC 2012

A. Transaction responsiveness B. Storage+query responsiveness C. Demand-supply responsiveness D. None
Answer: B. Storage+query responsiveness
Explanation: DW systems optimize large-scale storage and ad-hoc query performance.

512. Which DB abstraction level describes what data are stored?

Databases • DBMS Architecture • UGC NET Paper 2 Computer Science DEC 2012

A. Physical B. View C. Abstraction D. Logical
Answer: D. Logical
Explanation: Logical schema defines structure of stored data independent of physical storage.

513. For B+ tree on 8-byte names, 512-byte blocks, 4-byte pointers, best degree is

Databases • Index structures • UGC NET Paper 2 Computer Science DEC 2012

A. 16 B. 42 C. 43 D. 44
Answer: C. 43
Explanation: (512 B)/(8 B+4 B)≈42.6 pointers ⇒43 per node.

514. Schema R(A,B,C,D) with A→B, C→D decomposed into R₁(A,B), R₂(C,D) is:?

Databases • Normalization • UGC NET Paper 2 Computer Science DEC 2012

A. Dependency-preserving only B. Dependency-preserving+lossless C. Lossless only D. Lossless
Answer: B. Dependency-preserving+lossless
Explanation: Each FD preserved and intersection { } trivially ensures lossless join.

515. When a transaction updates then aborts leaving dirty writes, the problem is called:?

Databases • Transaction Anomalies • UGC NET Paper 2 Computer Science DEC 2012

A. Temporary Select B. Temporary Modify C. Dirty Read D. None
Answer: C. Dirty Read
Explanation: Reading uncommitted data leads to dirty reads when later aborted.

516. Based on cardinality and participation ________ associated with a relationship type, choose design.

Databases • Design • UGC NET Paper 2 Computer Science DEC 2012

A. Entity B. Constraints C. Rules D. Keys
Answer: B. Constraints
Explanation: Cardinality/participation constraints guide FK or cross-reference designs.

517. Which correct? I.2PL optimistic. II.2PL pessimistic. III.TS optimistic. IV.TS pessimistic.

Databases • Concurrency Control • UGC NET Paper 2 Computer Science DEC 2012

A. I & III B. II & IV C. I & IV D. II & III
Answer: B. II and IV
Explanation: Two-phase locking is pessimistic (locks before use); timestamping is optimistic (order by timestamps).

518. “Student marks ≤100” is a ___.

Databases • Constraints • UGC NET Paper 2 Computer Science DEC 2012

A. Integrity constraint B. Referential constraint C. Over-defined constraint D. Feasible constraint
Answer: A. Integrity constraint
Explanation: Domain integrity enforces attribute value limits.

519. Location transparency allows I.Users II.Programmers III.Managers to treat data as if at one location. Which?

Databases • Distributed DB • UGC NET Paper 2 Computer Science DEC 2012

A. I,II,III B. I,II only C. II,III only D. II only
Answer: A. I, II and III
Explanation: All stakeholders can access distributed data without regard to its physical location.

520. I.Recon in mixed frag is commutative. II.Vertical frag is commutative. Which?

Databases • Distributed DB • UGC NET Paper 2 Computer Science DEC 2012

A. I B. II C. Both D. None
Answer: C. Both are correct
Explanation: Both mixed and vertical fragmentation reconstructions commute when properly joined on keys.

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This quiz is for educational purposes only…

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Databases MCQs – Set 26

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