DA0-001 Mining and Acquiring Data Practice Question
This DA0-001 practice question tests your understanding of mining and acquiring data. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 marketing company is building a customer segmentation model. The data team has access to two sources: a CRM database with customer demographics and purchase history, and a third-party data provider that offers social media activity scores. The CRM data is updated daily, while the third-party data is refreshed weekly on Sundays. The analyst needs to create a unified dataset for the model training scheduled for Wednesday morning. The analyst runs a SQL query to join the two tables on CustomerID, but the resulting dataset has far fewer rows than expected. Upon investigation, the analyst finds that many customers in the CRM do not have matching records in the third-party data. Additionally, some customers in the third-party data have multiple entries due to unresolved duplicates. The analyst must produce the most complete dataset possible while maintaining data quality. Which course of action should the analyst take?
First deduplicate the third-party data by keeping the most recent record per CustomerID, then perform a LEFT JOIN from CRM to the deduplicated third-party data.
This preserves all CRM customers and handles duplicates correctly.
B
Perform an INNER JOIN on CustomerID and then remove duplicates from the result.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
First deduplicate the third-party data by keeping the most recent record per CustomerID, then perform a LEFT JOIN from CRM to the deduplicated third-party data.
Option A is correct because it first resolves the duplicate issue in the third-party data by keeping the most recent record per CustomerID, ensuring each customer has a single, current social media score. Then, a LEFT JOIN from CRM to the deduplicated third-party data preserves all CRM customers, maximizing completeness while maintaining data quality. This approach aligns with the goal of producing the most complete dataset for model training, as the CRM is the primary source with daily updates.
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.
✓
First deduplicate the third-party data by keeping the most recent record per CustomerID, then perform a LEFT JOIN from CRM to the deduplicated third-party data.
Why this is correct
This preserves all CRM customers and handles duplicates correctly.
Related concept
Read the scenario before looking for a memorised answer.
✗
Perform an INNER JOIN on CustomerID and then remove duplicates from the result.
Use only the third-party data because it provides the social media scores needed for segmentation.
Why it's wrong here
This excludes valuable CRM demographic and purchase data.
✗
Perform a LEFT JOIN from the third-party data to CRM, then aggregate duplicates by averaging scores.
Why it's wrong here
This would lose CRM customers without third-party match and averaging may not be appropriate.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose an INNER JOIN (Option B) thinking it ensures data quality by only including matched records, but they overlook the requirement for completeness, which necessitates preserving all CRM customers even without third-party matches.
Detailed technical explanation
How to think about this question
In SQL, a LEFT JOIN preserves all rows from the left table, so joining from CRM ensures no CRM customers are lost, even without third-party matches. Deduplication by keeping the most recent record per CustomerID relies on ordering by a timestamp column (e.g., last_updated) and using a window function like ROW_NUMBER() or a subquery with MAX(), which is a common pattern for handling slowly changing dimensions in data warehousing. This approach maintains referential integrity and avoids the pitfalls of averaging duplicate scores, which could skew the model's input features.
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.
Mining and Acquiring Data — This question tests Mining and Acquiring Data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: First deduplicate the third-party data by keeping the most recent record per CustomerID, then perform a LEFT JOIN from CRM to the deduplicated third-party data. — Option A is correct because it first resolves the duplicate issue in the third-party data by keeping the most recent record per CustomerID, ensuring each customer has a single, current social media score. Then, a LEFT JOIN from CRM to the deduplicated third-party data preserves all CRM customers, maximizing completeness while maintaining data quality. This approach aligns with the goal of producing the most complete dataset for model training, as the CRM is the primary source with daily updates.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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