DS0-001 Database Structures And SQL Practice Question
A database developer needs to combine the results of two different SELECT queries into a single result set. Which operator should be used?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
UNION
The UNION operator is specifically designed to combine the result sets of two or more SELECT statements into one.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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JOIN
Why it's wrong here
JOIN combines rows based on a related column, not the result sets themselves.
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CONCAT
Why it's wrong here
CONCAT combines strings.
- ✓
UNION
Why this is correct
UNION stacks results of multiple queries.
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MERGE
Why it's wrong here
MERGE is used for inserting/updating data based on a match.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official CompTIA exam blueprint
This DS0-001 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DS0-001 exam.