- A
LEFT JOIN
LEFT JOIN returns all rows from the left (employees) table.
- B
INNER JOIN
Why wrong: INNER JOIN returns only rows with matching keys in both tables.
- C
CROSS JOIN
Why wrong: CROSS JOIN creates a Cartesian product, not a conditional join.
- D
RIGHT JOIN
Why wrong: RIGHT JOIN returns all rows from the right table; employees would need to be on the right.
- E
FULL OUTER JOIN
FULL OUTER JOIN returns all rows from both tables, including all employees.
Question 475 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 is performing a join between two tables: 'employees' and 'departments'. The 'employees' table has a foreign key 'dept_id' referencing the 'departments' table. Which two join types would include all rows from the 'employees' table, regardless of whether there is a matching department? (Select TWO)
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
✓
LEFT JOIN
LEFT JOIN and RIGHT JOIN (if reversed) can include all rows from the left table. Specifically, LEFT JOIN includes all rows from the left table. FULL OUTER JOIN also includes all rows from both tables, but the question says 'all rows from the employees table' – that is satisfied by LEFT JOIN and also by FULL OUTER JOIN (which includes all from employees). However, the correct answer set: LEFT JOIN and FULL OUTER JOIN. The question says 'include all rows from the employees table' – RIGHT JOIN does not guarantee that unless employees is on the right side. So the correct two are LEFT JOIN and FULL OUTER JOIN.
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.
- ✓
LEFT JOIN
Why this is correct
LEFT JOIN returns all rows from the left (employees) table.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
INNER JOIN
Why it's wrong here
INNER JOIN returns only rows with matching keys in both tables.
- ✗
CROSS JOIN
Why it's wrong here
CROSS JOIN creates a Cartesian product, not a conditional join.
- ✗
RIGHT JOIN
Why it's wrong here
RIGHT JOIN returns all rows from the right table; employees would need to be on the right.
- ✓
FULL OUTER JOIN
Why this is correct
FULL OUTER JOIN returns all rows from both tables, including all employees.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 DA0-001 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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: LEFT JOIN — LEFT JOIN and RIGHT JOIN (if reversed) can include all rows from the left table. Specifically, LEFT JOIN includes all rows from the left table. FULL OUTER JOIN also includes all rows from both tables, but the question says 'all rows from the employees table' – that is satisfied by LEFT JOIN and also by FULL OUTER JOIN (which includes all from employees). However, the correct answer set: LEFT JOIN and FULL OUTER JOIN. The question says 'include all rows from the employees table' – RIGHT JOIN does not guarantee that unless employees is on the right side. So the correct two are LEFT JOIN and FULL OUTER JOIN.
What should I do if I get this DA0-001 question wrong?
Identify which DA0-001 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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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