The answer is to include missing fields as null in the JSON object. This is the best practice for handling missing data in JSON denormalization because it preserves the defined schema structure while explicitly signaling the absence of a value, allowing downstream systems to apply their own null-handling logic without ambiguity. On the CompTIA Data+ DA0-001 exam, this scenario tests your understanding of data integrity during ETL transformations—specifically that placeholder strings like "N/A" or empty strings can be misinterpreted as valid data, and that omitting keys entirely breaks the JSON contract. A common trap is choosing to omit missing fields to save space, but that forces consuming applications to check for key existence rather than a null value. Memory tip: think of JSON null as a reserved parking spot—it keeps the structure intact so everyone knows exactly where the missing car should be.
DA0-001 Comparing and Contrasting Data Concepts Practice Question
This DA0-001 practice question tests your understanding of comparing and contrasting data concepts. 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 mid-sized e-commerce company stores customer data in a relational database. The database has a table named 'Customers' with columns: CustomerID (primary key), FirstName, LastName, Email, Phone, Address, City, State, ZipCode, and SignUpDate. The company is migrating to a new CRM system that requires a denormalized structure for performance reasons. The new system expects a single table 'CustomerDetails' with columns: CustomerID, FullName (concatenation of first and last name), ContactInfo (JSON object containing email, phone, and address), SignUpDate, and Region (derived from state). The data analyst must design an ETL process to transform the data. During a test run, the analyst notices that some records have missing Phone or Address values. Which of the following is the best approach to handle missing data in the ContactInfo JSON object?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Include the missing fields as null in the JSON object.
Option C is correct because representing missing fields as null in the JSON object preserves the data structure and allows downstream systems to explicitly handle null values. This approach maintains data integrity without discarding records or introducing ambiguous placeholder strings that could be misinterpreted as actual data.
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.
✗
Exclude any record with missing Phone or Address from the migration.
Why it's wrong here
Loses data unnecessarily.
✗
Set missing values to an empty string in the JSON object.
Why it's wrong here
Empty string is ambiguous and may cause errors.
✓
Include the missing fields as null in the JSON object.
Why this is correct
Null explicitly indicates missing data.
Clue confirmation
The clue words "best", "first", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Replace missing values with 'N/A' string.
Why it's wrong here
'N/A' is a placeholder that could be misinterpreted as a valid value.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse 'handling missing data' with 'filling in missing data,' leading them to choose placeholder strings (B or D) instead of preserving the null representation that JSON natively supports.
Detailed technical explanation
How to think about this question
In JSON, null is a distinct data type that explicitly indicates the absence of a value, whereas an empty string is a valid string value. When the CRM system processes the ContactInfo JSON, it can use null checks (e.g., `if (json.phone === null)`) to trigger default behaviors or error handling, avoiding false positives from placeholder strings. This aligns with best practices for ETL transformations where missing data should be preserved as null to maintain semantic accuracy.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Comparing and Contrasting Data Concepts — This question tests Comparing and Contrasting Data Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Include the missing fields as null in the JSON object. — Option C is correct because representing missing fields as null in the JSON object preserves the data structure and allows downstream systems to explicitly handle null values. This approach maintains data integrity without discarding records or introducing ambiguous placeholder strings that could be misinterpreted as actual data.
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: "best", "first", "primary". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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