- A
INNER JOIN
INNER JOIN returns only matching rows, which are customers with orders.
- B
LEFT JOIN
Why wrong: LEFT JOIN returns all customers, even those without orders.
- C
FULL OUTER JOIN
Why wrong: FULL OUTER JOIN returns all rows from both tables, including non-matching.
- D
RIGHT JOIN
Why wrong: RIGHT JOIN returns all orders, but we need only customers with orders.
Question 27 of 1,000
DA0-001 Data Concepts and Environments Practice Question
This DA0-001 practice question tests your understanding of data concepts and environments. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A data analyst needs to combine customer data from two tables: Customers (CustomerID, Name) and Orders (OrderID, CustomerID, Amount). Only customers who have placed at least one order should be included. Which JOIN type should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"least"Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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
✓
INNER JOIN
An INNER JOIN returns only rows where there is a match in both tables. Since the requirement is to include only customers who have placed at least one order, the INNER JOIN on CustomerID will filter out any customer without a matching order record, exactly meeting the condition.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
INNER JOIN
Why this is correct
INNER JOIN returns only matching rows, which are customers with orders.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
LEFT JOIN
Why it's wrong here
LEFT JOIN returns all customers, even those without orders.
- ✗
FULL OUTER JOIN
Why it's wrong here
FULL OUTER JOIN returns all rows from both tables, including non-matching.
- ✗
RIGHT JOIN
Why it's wrong here
RIGHT JOIN returns all orders, but we need only customers with orders.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose LEFT JOIN thinking it 'includes all customers' without realizing it also includes customers with no orders, which fails the explicit condition of 'only customers who have placed at least one order'.
Detailed technical explanation
How to think about this question
Under the hood, an INNER JOIN performs a hash or nested-loop join on the join key (CustomerID), discarding non-matching rows from both tables. In real-world scenarios, this is critical for data integrity when generating reports like 'active customer sales' where unmatched records would skew aggregations or cause NULL-handling issues.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the DA0-001 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Data Concepts and Environments — study guide chapter
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FAQ
Questions learners often ask
What does this DA0-001 question test?
Data Concepts and Environments — This question tests Data Concepts and Environments — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: INNER JOIN — An INNER JOIN returns only rows where there is a match in both tables. Since the requirement is to include only customers who have placed at least one order, the INNER JOIN on CustomerID will filter out any customer without a matching order record, exactly meeting the condition.
What should I do if I get this DA0-001 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This DA0-001 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 DA0-001 exam.
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