Computer Knowledge - MCQ Practice Questions

Elasticity allows automatic resource provisioning and de-provisioning based on real-time demand, reducing costs.

GROUP BY groups rows with identical values in specified columns, used with aggregate functions like COUNT(), SUM().

3NF (Third Normal Form) ensures all non-key attributes depend only on the primary key, eliminating transitive dependencies.

Quicksort's worst-case complexity is O(n²) when pivot selection is poor, though average case is O(n log n).

PaaS (Platform as a Service) provides a platform to develop and deploy applications without managing underlying infrastructure.

TRUNCATE is DDL (immediate, cannot be rolled back in most databases), DELETE is DML (slower, can be rolled back).

Dijkstra's algorithm efficiently finds shortest paths from a source node to all other nodes in weighted graphs with non-negative weights.

Normalization scales features (e.g., 0-1 range) preventing features with larger scales from dominating model training.

SQL injection exploits vulnerable input handling to execute unintended SQL commands, potentially exposing or modifying data.

Supervised learning trains on labeled data (features + targets); unsupervised finds patterns in unlabeled data without predefined outputs.

Consensus algorithms (like Raft, Paxos) enable distributed systems to reliably agree on state even with node failures.

The CAP theorem shows it's impossible to guarantee all three: Consistency, Availability, and Partition tolerance simultaneously.

Activation functions (ReLU, sigmoid, tanh) add non-linearity, allowing neural networks to approximate non-linear relationships.

3NF eliminates partial and transitive dependencies, making it the standard for practical database design. BCNF is stricter but 3NF is the most commonly implemented normalization form.

NoSQL databases like MongoDB and Cassandra are designed for horizontal scaling and flexible schemas, making them ideal for cloud-based big data applications with varying data structures.

B+ Tree indexes maintain sorted order and support efficient range queries, point queries, and prefix searches. Hash indexes are faster for exact matches but cannot handle range queries efficiently.

Data warehouses use materialized views to pre-aggregate data and strategic denormalization for faster analytical queries. These techniques significantly improve performance on large fact tables.

Cloud-native NoSQL databases prioritize availability and partition tolerance (CAP theorem), implementing eventual consistency to handle distributed system challenges while maintaining horizontal scalability.

SQL injection occurs when untrusted input is concatenated into SQL queries. Parameterized queries/prepared statements separate code from data, preventing attackers from modifying query logic.

Shard key selection determines data distribution and performance. Poor shard key choices lead to hotspots, uneven load distribution, and performance degradation across the sharded cluster.