Database/SQL
Which normal form eliminates transitive dependencies in a database table?
A
Third Normal Form (3NF)
B
Second Normal Form (2NF)
C
Boyce-Codd Normal Form (BCNF)
D
First Normal Form (1NF)
Correct Answer:
A. Third Normal Form (3NF)
Explanation:
3NF removes transitive dependencies where a non-key attribute depends on another non-key attribute. BCNF is stricter but 3NF is the standard answer for eliminating transitive dependencies.
What is the time complexity of a binary search algorithm on a sorted array?
A
O(n)
B
O(log n)
C
O(n²)
D
O(n log n)
Correct Answer:
B. O(log n)
Explanation:
Binary search divides the search space in half with each iteration, resulting in logarithmic time complexity O(log n).
Which SQL command is used to remove a table structure along with its data?
A
DELETE
B
DROP
C
TRUNCATE
D
REMOVE
Explanation:
DROP removes the entire table structure and data. DELETE removes only data. TRUNCATE removes data but is faster than DELETE.
In a hash table, what is the primary cause of collision?
A
Two different keys hashing to the same index
B
Insufficient memory allocation
C
Poor sorting algorithm
D
Network latency issues
Correct Answer:
A. Two different keys hashing to the same index
Explanation:
Hash collisions occur when two different keys hash to the same table index. Resolution techniques include chaining and open addressing.
Which of the following is NOT a characteristic of a relational database?
A
Uses tables with rows and columns
B
Enforces ACID properties
C
Supports unstructured data storage by default
D
Uses primary keys for unique identification
Correct Answer:
C. Supports unstructured data storage by default
Explanation:
Relational databases store structured data in tables. Unstructured data is typically stored in NoSQL or document databases.
What does the acronym ACID stand for in database transactions?
A
Atomicity, Consistency, Isolation, Durability
B
Access, Control, Integration, Distribution
C
Accuracy, Completeness, Integrity, Detection
D
Authorization, Concurrency, Indexing, Duration
Correct Answer:
A. Atomicity, Consistency, Isolation, Durability
Explanation:
ACID properties ensure reliable database transactions: Atomicity (all-or-nothing), Consistency (valid state), Isolation (concurrent independence), Durability (permanent storage).
Which data structure is best suited for implementing a priority queue?
A
Stack
B
Queue
C
Heap
D
Linked List
Explanation:
A heap (binary heap) efficiently implements priority queues with O(log n) insertion and deletion of minimum/maximum elements.
In SQL, what is the difference between INNER JOIN and LEFT JOIN?
A
INNER JOIN returns all rows; LEFT JOIN returns only matching rows
B
INNER JOIN returns only matching rows; LEFT JOIN returns all rows from left table
C
Both are identical in functionality
D
INNER JOIN is faster than LEFT JOIN always
Correct Answer:
B. INNER JOIN returns only matching rows; LEFT JOIN returns all rows from left table
Explanation:
INNER JOIN returns only rows with matches in both tables. LEFT JOIN returns all rows from the left table plus matching rows from the right table.
Which cloud service model provides virtualized computing resources over the internet?
A
SaaS (Software as a Service)
B
IaaS (Infrastructure as a Service)
C
PaaS (Platform as a Service)
D
DaaS (Database as a Service)
Correct Answer:
B. IaaS (Infrastructure as a Service)
Explanation:
IaaS provides infrastructure resources (compute, storage, networking). SaaS provides applications, PaaS provides development platforms.
What is the primary purpose of database indexing?
A
Increase storage space
B
Improve query performance
C
Reduce security vulnerabilities
D
Eliminate data redundancy
Correct Answer:
B. Improve query performance
Explanation:
Indexes speed up data retrieval by creating optimized lookup structures, reducing the number of disk accesses needed to find data.
