In C, which operator has the highest precedence?

The correct answer is C: Parentheses (). Parentheses have the highest precedence in C. Expressions within parentheses are evaluated first, followed by arithmetic operators, then logical operators, and finally assignment operators.

Which of the following is a non-relational database designed for handling unstructured data at scale?

The correct answer is A: MongoDB. MongoDB is a NoSQL document database that handles unstructured and semi-structured data efficiently, unlike relational databases like PostgreSQL, Oracle, and MySQL.

Consider: int *p, q; What is the type of q?

The correct answer is B: Integer. Only p is declared as a pointer (int *p). The variable q is declared as a regular integer (int q). The * applies only to p in this declaration.

Consider a structure with bit fields. What will be the size of the following structure in bytes? struct demo { unsigned int a : 5; unsigned int b : 3; unsigned int c : 4; unsigned int d : 7; };

The correct answer is C: 4 bytes. Bit fields in C are packed into the smallest integral type that can accommodate them. Here, a(5) + b(3) + c(4) + d(7) = 19 bits total. Since 19 bits exceed 16 bits but fit within 32 bits, the compiler allocates 4 bytes (32 bits) for this structure, following standard packing rules.

Which operator is used to access the value at an address in C?

The correct answer is B: *. The * operator is the dereference operator that accesses the value at a memory address. The & operator gets the address of a variable.

Corporate & IT Interview Preparation

Q.141 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)

Correct Answer: B. O(n²)

Explanation:

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

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Q.142 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

Correct Answer: B. PaaS

Explanation:

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

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Q.143 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).

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Q.144 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.

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Q.145 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.

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Q.146 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.

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Q.147 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.

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Q.148 Medium Database/SQL

In database indexing, which type of index structure provides the best average-case performance for range queries in modern database systems?

A Hash Index

B B+ Tree Index

C Bitmap Index

D Full-text Index

Correct Answer: B. B+ Tree Index

Explanation:

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.

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Q.149 Medium Database/SQL

Which of the following SQL query optimization techniques is most effective when dealing with large fact tables in a data warehouse environment?

A Using UNION instead of UNION ALL

B Materialized views and denormalization

C Increasing the number of JOINs in queries

D Using correlated subqueries for filtering

Correct Answer: B. Materialized views and denormalization

Explanation:

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.

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Q.150 Medium Database/SQL

In the context of distributed databases, which consistency model is used by most cloud-native databases like DynamoDB and offers eventual consistency?

A Strong Consistency

B Causal Consistency

C Eventual Consistency

D Linearizability

Correct Answer: C. Eventual Consistency

Explanation:

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

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