A Primary Key in RDBMS must be: MCQ with Answer and Explanation

Question
A Primary Key in RDBMS must be:
A. Can have null values
B. Unique and not null
C. Always a foreign key
D. Duplicate values allowed
Answer: Option B
Solution (By JKSSB Mock Tests)
A primary key uniquely identifies each record and cannot contain null values.
This question belongs to: Computer Database Management System (DBMS)
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Practice More Database Management System (DBMS) Questions

Question #1
Which of the following database models organizes data in a tree-like upside-down structure with parent-child relationships?
A. Relational Model
B. Object-Oriented Model
C. Hierarchical Model
D. Network Model
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Correct Answer: Option C

Explanation:
The Hierarchical Model stores data in a tree-like configuration where each child node has exactly one parent node.
This question belongs to: Computer Database Management System (DBMS)
Question #2
What is the main purpose of indexing in a database?
A. To encrypt data
B. To backup data
C. To delete data
D. To speed up data retrieval
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Correct Answer: Option D

Explanation:
Indexes improve the speed of data retrieval operations on a database table.
This question belongs to: Computer Database Management System (DBMS)
Question #3
What is a query optimizer in a DBMS?
A. A component that determines the most efficient way to execute a query
B. A backup utility
C. A tool for indexing
D. A user interface
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Correct Answer: Option A

Explanation:
The query optimizer analyzes SQL queries and selects the most efficient execution plan based on statistics and indexes.
This question belongs to: Computer Database Management System (DBMS)
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