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Computer Knowledge

Campus placement MCQ questions — Aptitude, Verbal, Reasoning, Technical.

309 Q 4 Subjects Any Graduate
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Difficulty: All Easy Medium Hard 51–60 of 309
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Q.51 Medium Computer Knowledge Database/SQL
Which data structure is most efficient for implementing a LRU (Least Recently Used) cache?
A Array
B Hash Map + Doubly Linked List
C Binary Search Tree
D Queue only
Correct Answer:  B. Hash Map + Doubly Linked List
EXPLANATION

Hash Map provides O(1) lookup while Doubly Linked List maintains insertion order and allows O(1) removal/reordering.

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Q.52 Medium Computer Knowledge Database/SQL
In SQL, what is the difference between HAVING and WHERE clauses?
A Both serve identical purposes
B WHERE filters rows before grouping; HAVING filters groups after aggregation
C HAVING is used for individual row filtering
D WHERE can only be used with JOIN operations
Correct Answer:  B. WHERE filters rows before grouping; HAVING filters groups after aggregation
EXPLANATION

WHERE clause filters individual rows before GROUP BY, while HAVING filters aggregated groups after GROUP BY.

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Q.53 Medium Computer Knowledge Database/SQL
What does CAP theorem state about distributed database systems?
A All three properties can be achieved simultaneously
B Only two of Consistency, Availability, and Partition tolerance can be guaranteed
C Consistency is always sacrificed first
D Partition tolerance is optional in modern systems
Correct Answer:  B. Only two of Consistency, Availability, and Partition tolerance can be guaranteed
EXPLANATION

CAP theorem proves that distributed systems can guarantee at most 2 of 3 properties: Consistency, Availability, and Partition tolerance.

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Q.54 Medium Computer Knowledge Database/SQL
Which of the following is NOT a characteristic of relational databases?
A ACID compliance
B Flexible schema
C Structured data storage
D Data integrity constraints
Correct Answer:  B. Flexible schema
EXPLANATION

Relational databases have fixed schemas. Flexible schemas are a characteristic of NoSQL databases like MongoDB.

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Q.55 Easy Computer Knowledge Database/SQL
In the OSI model, which layer is responsible for routing and logical addressing?
A Physical Layer
B Data Link Layer
C Network Layer
D Transport Layer
Correct Answer:  C. Network Layer
EXPLANATION

The Network Layer (Layer 3) handles routing, IP addressing, and logical path determination for data packets.

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Q.56 Easy Computer Knowledge Database/SQL
What is the primary purpose of indexing in databases?
A To reduce storage space
B To speed up data retrieval operations
C To enforce data integrity
D To manage concurrent access
Correct Answer:  B. To speed up data retrieval operations
EXPLANATION

Indexes create a faster lookup structure similar to a book's index, enabling rapid data retrieval without full table scans.

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Q.57 Easy Computer Knowledge Database/SQL
Which algorithm has O(n log n) time complexity and is preferred for large datasets in modern databases?
A Bubble Sort
B Merge Sort
C Selection Sort
D Insertion Sort
Correct Answer:  B. Merge Sort
EXPLANATION

Merge Sort maintains O(n log n) complexity in all cases and is stable, making it ideal for sorting large datasets.

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Q.58 Easy Computer Knowledge Database/SQL
In a relational database, what does normalization primarily aim to eliminate?
A NULL values
B Data redundancy and anomalies
C Foreign key constraints
D Index creation
Correct Answer:  B. Data redundancy and anomalies
EXPLANATION

Normalization removes data redundancy and prevents update, insertion, and deletion anomalies through organized table structures.

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Q.59 Easy Computer Knowledge Database/SQL
What is the primary advantage of using INNER JOIN over OUTER JOIN in SQL?
A It processes faster for small datasets
B It returns only matching records from both tables
C It uses less memory than OUTER JOIN
D It can handle NULL values better
Correct Answer:  B. It returns only matching records from both tables
EXPLANATION

INNER JOIN returns only rows that have matching values in both tables, making queries more efficient for specific requirements.

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Q.60 Easy Computer Knowledge Database/SQL
Which of the following is a ACID property that ensures all or nothing transaction execution?
A Atomicity
B Consistency
C Isolation
D Durability
Correct Answer:  A. Atomicity
EXPLANATION

Atomicity ensures that a transaction is treated as a single unit - either all operations complete or none do.

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