Computer Knowledge — Database/SQL Questions & Answers

Q.1 Easy Database/SQL

Which of the following represents a vulnerability in SQL query construction that can be exploited through malicious user input, and can be prevented using parameterized queries?

A Buffer overflow attacks

B Cross-site scripting (XSS)

C SQL injection attacks

D Distributed denial of service (DDoS)

Correct Answer: C. SQL injection attacks

EXPLANATION

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.

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Q.2 Easy Database/SQL

Which of the following is a characteristic of NoSQL databases that makes them suitable for handling big data in cloud environments?

A Strict ACID compliance across all nodes

B Horizontal scalability and schema-less design

C Requirement for predefined schemas before insertion

D Complex JOIN operations for data retrieval

Correct Answer: B. Horizontal scalability and schema-less design

EXPLANATION

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.

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Q.3 Easy Database/SQL

In a relational database, which normal form eliminates partial dependencies and is considered essential for most practical database designs?

A Second Normal Form (2NF)

B Third Normal Form (3NF)

C Boyce-Codd Normal Form (BCNF)

D Fourth Normal Form (4NF)

Correct Answer: B. Third Normal Form (3NF)

EXPLANATION

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.

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Q.4 Easy Database/SQL

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().

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Q.5 Easy Database/SQL

What is the main advantage of cloud computing's elasticity?

A Lower initial hardware cost

B Automatic resource scaling based on demand

C Guaranteed 100% uptime

D Elimination of all security risks

Correct Answer: B. Automatic resource scaling based on demand

EXPLANATION

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

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Q.6 Easy Database/SQL

Which data structure is best for implementing a priority queue in heapsort algorithm?

A Stack

B Queue

C Heap

D Array

Correct Answer: C. Heap

EXPLANATION

A heap (min-heap or max-heap) efficiently supports priority queue operations with O(log n) insertion and deletion.

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Q.7 Easy Database/SQL

In database indexing, which structure provides O(log n) search complexity?

A Linear search

B B-Tree

C Hash table with collision

D Linked list

Correct Answer: B. B-Tree

EXPLANATION

B-Tree maintains balanced structure ensuring O(log n) search, insert, and delete operations, commonly used in databases.

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Q.8 Easy Database/SQL

Which SQL JOIN returns only matching records from both tables?

A INNER JOIN

B LEFT JOIN

C RIGHT JOIN

D FULL OUTER JOIN

Correct Answer: A. INNER JOIN

EXPLANATION

INNER JOIN returns only the records that have matching values in both tables, filtering out non-matching rows.

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Q.9 Easy Database/SQL

Which cryptographic algorithm is currently recommended by NIST for symmetric encryption?

A DES (Data Encryption Standard)

B AES (Advanced Encryption Standard)

C MD5

D SHA-1

Correct Answer: B. AES (Advanced Encryption Standard)

EXPLANATION

AES is the current NIST standard for symmetric encryption with key sizes of 128, 192, or 256 bits. DES is deprecated due to weak key size.

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Q.10 Easy Database/SQL

What is the purpose of the COMMIT statement in SQL transactions?

A To undo all pending changes

B To save all changes made during a transaction permanently to the database

C To create a new transaction

D To delete committed records

Correct Answer: B. To save all changes made during a transaction permanently to the database

EXPLANATION

COMMIT saves all changes made during the current transaction to the database permanently. Until COMMIT, changes can be rolled back using ROLLBACK.

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