In SQL, which JOIN returns only matching records from both tables?
A
INNER JOIN
B
LEFT JOIN
C
FULL OUTER JOIN
D
CROSS JOIN
Correct Answer:
A. INNER JOIN
Explanation:
INNER JOIN returns only rows with matching values in both tables. LEFT JOIN includes unmatched left table rows, FULL OUTER JOIN includes all rows, and CROSS JOIN produces Cartesian product.
What is the time complexity of searching in a balanced binary search tree?
A
O(log n)
B
O(n)
C
O(n log n)
D
O(1)
Correct Answer:
A. O(log n)
Explanation:
Balanced BSTs (AVL, Red-Black) maintain O(log n) search time by keeping height logarithmic. Unbalanced trees degrade to O(n) in worst case.
In cloud computing, what does IaaS stand for?
A
Infrastructure as a Service
B
Integration as a Service
C
Intelligent as a Service
D
Internal as a Service
Correct Answer:
A. Infrastructure as a Service
Explanation:
IaaS provides virtualized computing resources over the internet (AWS EC2, Azure VMs). PaaS and SaaS are higher-level abstractions.
In cybersecurity, what is the primary purpose of a firewall?
A
Control incoming and outgoing network traffic based on rules
B
Encrypt all data transmitted
C
Detect viruses and malware
D
Manage user authentication
Correct Answer:
A. Control incoming and outgoing network traffic based on rules
Explanation:
Firewalls filter traffic based on security policies. While they provide protection, encryption is separate, antivirus is different, and authentication is handled by other systems.
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.
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.
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.
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.
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.
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.
