Which SQL set operator combines the output of two queries but preserves all duplicate rows without filtering them? MCQ with Answer and Explanation

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Which SQL set operator combines the output of two queries but preserves all duplicate rows without filtering them?

A. UNION ALL

B. INTERSECT

C. UNION

D. MINUS

Answer: Option A

Solution (By JKSSB Mock Tests)

UNION ALL appends the results of multiple SELECT queries together without performing any deduplication, making it faster than UNION.

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 type of database backup?

A. Differential backup

B. All of the above

C. Incremental backup

D. Full backup

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Correct Answer: Option B

Explanation:
Full, incremental, and differential backups are common backup strategies.

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

Question #2

Which normal form eliminates transitive dependencies?

A. 1NF

B. BCNF

C. 3NF

D. 2NF

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Correct Answer: Option C

Explanation:
Third Normal Form (3NF) removes transitive dependencies on non-prime attributes.

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

Question #3

Which type of subquery executes once for each row evaluated by the outer query, depending on values provided by the outer statement?

A. Correlated Subquery

B. Static Subquery

C. Independent Subquery

D. Scalar Subquery

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Correct Answer: Option A

Explanation:
A Correlated Subquery is an inner query that references columns from the outer query, meaning it must be executed repeatedly for each row evaluated by the outer query.

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

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