Showing 291–300 of 309 questions
In SQL, what does the GROUP BY clause do?
A
Joins multiple tables
B
Aggregates rows into groups based on specified columns
C
Deletes duplicate records
D
Orders results alphabetically
Correct Answer:
B. Aggregates rows into groups based on specified columns
Explanation:
GROUP BY groups rows with identical values in specified columns, used with aggregate functions like COUNT(), SUM().
Q.292
Medium
Database/SQL
Which normalization form eliminates all non-key dependencies?
Explanation:
3NF (Third Normal Form) ensures all non-key attributes depend only on the primary key, eliminating transitive dependencies.
Q.293
Medium
Database/SQL
What is the time complexity of quicksort algorithm in the worst case?
A
O(n log n)
B
O(n²)
C
O(n)
D
O(log n)
Explanation:
Quicksort's worst-case complexity is O(n²) when pivot selection is poor, though average case is O(n log n).
Q.294
Medium
Database/SQL
In cloud computing, which service model allows customers to run their own applications but not manage infrastructure?
A
IaaS
B
PaaS
C
SaaS
D
DBaaS
Explanation:
PaaS (Platform as a Service) provides a platform to develop and deploy applications without managing underlying infrastructure.
Q.295
Medium
Database/SQL
What is the difference between DELETE and TRUNCATE in SQL?
A
DELETE is faster than TRUNCATE
B
TRUNCATE is DDL; DELETE is DML and is slower but can be rolled back
C
TRUNCATE cannot be rolled back while DELETE can
D
Both have identical functionality
Correct Answer:
B. TRUNCATE is DDL; DELETE is DML and is slower but can be rolled back
Explanation:
TRUNCATE is DDL (immediate, cannot be rolled back in most databases), DELETE is DML (slower, can be rolled back).
Q.296
Medium
Database/SQL
In graph algorithms, which algorithm finds the shortest path in weighted graphs?
A
DFS
B
BFS
C
Dijkstra's algorithm
D
Topological sort
Correct Answer:
C. Dijkstra's algorithm
Explanation:
Dijkstra's algorithm efficiently finds shortest paths from a source node to all other nodes in weighted graphs with non-negative weights.
Q.297
Medium
Database/SQL
What does normalization in machine learning context primarily aim to achieve?
A
Reduce features to 2D
B
Scale features to similar ranges to improve model performance
C
Remove all outliers
D
Increase dataset size
Correct Answer:
B. Scale features to similar ranges to improve model performance
Explanation:
Normalization scales features (e.g., 0-1 range) preventing features with larger scales from dominating model training.
Q.298
Medium
Database/SQL
In cybersecurity, what is SQL injection attack?
A
Inserting legitimate SQL into database
B
Malicious SQL code injected into input fields to manipulate database queries
C
A method to optimize SQL performance
D
Splitting SQL statements across multiple lines
Correct Answer:
B. Malicious SQL code injected into input fields to manipulate database queries
Explanation:
SQL injection exploits vulnerable input handling to execute unintended SQL commands, potentially exposing or modifying data.
Q.299
Medium
Database/SQL
What is the primary difference between supervised and unsupervised machine learning?
A
Supervised uses labeled data; unsupervised uses unlabeled data
B
Unsupervised is faster than supervised
C
Supervised cannot predict outcomes
D
Unsupervised requires human supervision
Correct Answer:
A. Supervised uses labeled data; unsupervised uses unlabeled data
Explanation:
Supervised learning trains on labeled data (features + targets); unsupervised finds patterns in unlabeled data without predefined outputs.
In distributed systems, what is a consensus algorithm primarily used for?
A
Encrypting data
B
Ensuring all nodes agree on a single value despite failures
C
Compressing database files
D
Load balancing across servers
Correct Answer:
B. Ensuring all nodes agree on a single value despite failures
Explanation:
Consensus algorithms (like Raft, Paxos) enable distributed systems to reliably agree on state even with node failures.
