What is a self join? MCQ with Answer and Explanation

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What is a self join?

A. Joining two different tables

B. Joining tables without a common column

C. Joining more than two tables

D. Joining a table with itself

Answer: Option D

Solution (By JKSSB Mock Tests)

A self join is a join where a table is joined with itself, often used to compare rows within the same table.

This question belongs to: Computer Database Management System (DBMS)

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Question #1

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The actual collection of data tuples stored in a table at any specific point in time is called a what?

A. Relation Instance

B. Relation Schema

C. Relation Domain

D. Relation Degree

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Correct Answer: Option A

Explanation:
A Relation Instance is the specific collection of data rows (tuples) present in a table at a given moment. It changes frequently as data is modified.

This question belongs to: Computer Database Management System (DBMS)

Question #2

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What is a data dictionary in a DBMS?

A. A repository of metadata about the database

B. A log file

C. A table containing user data

D. A backup of the database

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Correct Answer: Option A

Explanation:
The data dictionary stores metadata such as table definitions, column types, constraints, and other database objects.

This question belongs to: Computer Database Management System (DBMS)

Question #3

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What is the purpose of the SQL GROUP BY ... HAVING combination?

A. To filter groups based on aggregate values

B. To join groups

C. To sort groups

D. To select individual rows

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Correct Answer: Option A

Explanation:
HAVING is used in conjunction with GROUP BY to filter groups based on conditions applied to aggregate functions.

This question belongs to: Computer Database Management System (DBMS)

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