What is the purpose of the SQL 'UNION' operator? MCQ with Answer and Explanation

Question
What is the purpose of the SQL 'UNION' operator?
A. To join tables horizontally
B. To filter duplicates
C. To combine the results of two or more SELECT statements, removing duplicates
D. To aggregate data
Answer: Option C
Solution (By JKSSB Mock Tests)
UNION concatenates the result sets of two or more queries, eliminating duplicate rows. UNION ALL keeps duplicates.
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 is a DCL (Data Control Language) command?
A. CREATE
B. COMMIT
C. GRANT
D. SELECT
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Correct Answer: Option C

Explanation:
GRANT and REVOKE are DCL commands. COMMIT is TCL, SELECT is DML, CREATE is DDL.
This question belongs to: Computer Database Management System (DBMS)
Question #2
Information is:
A. Hardware component
B. Processed and meaningful form of data
C. Raw facts and figures
D. Programming code
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Correct Answer: Option B

Explanation:
Information is data that has been organized and processed to provide context and meaning.
This question belongs to: Computer Database Management System (DBMS)
Question #3
Which normal form requires that all attributes in a table contain only atomic, indivisible values, and prohibits multi-valued attributes?
A. Boyce-Codd Normal Form (BCNF)
B. Second Normal Form (2NF)
C. Third Normal Form (3NF)
D. First Normal Form (1NF)
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Correct Answer: Option D

Explanation:
A relation is in First Normal Form (1NF) if and only if the domain of every attribute contains only atomic (indivisible) values, and no repeating groups exist.
This question belongs to: Computer Database Management System (DBMS)
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