This DP-300 practice question tests your understanding of implement a secure environment. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You are responsible for an Azure SQL Database that stores customer personally identifiable information (PII). You need to ensure that users with the 'CustomerService' role can see only the last four digits of Social Security numbers. Which feature should you use?
Row-Level Security
Why wrong: Controls rows, not columns.
Column-level security with DENY permission on the column
Why wrong: Denies access entirely, not partial.
Dynamic Data Masking with a partial mask function
Masks the column to show only last four digits.
Always Encrypted with deterministic encryption
Why wrong: Encrypts data, but does not mask partial values.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Dynamic Data Masking with a partial mask function
Dynamic Data Masking (DDM) with a partial mask function is the correct choice because it allows you to obfuscate sensitive data at query time without altering the underlying storage. For a Social Security number, you can apply a mask like 'partial(0, "XXX-XX-", 4)' to expose only the last four digits to users in the 'CustomerService' role, while the full value remains intact in the database.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Row-Level Security
Why it's wrong here
Controls rows, not columns.
Column-level security with DENY permission on the column
Why it's wrong here
Denies access entirely, not partial.
Dynamic Data Masking with a partial mask function
Why this is correct
Masks the column to show only last four digits.
Related concept
Read the scenario before looking for a memorised answer.
Always Encrypted with deterministic encryption
Why it's wrong here
Encrypts data, but does not mask partial values.
Common exam traps
The trap here is that candidates often confuse Dynamic Data Masking with column-level permissions or Always Encrypted, mistakenly thinking that hiding the column entirely or encrypting it meets the requirement of showing a partial value, when in fact DDM is the only feature designed to expose a masked version of data without altering the underlying storage or access permissions.
Detailed technical explanation
Dynamic Data Masking works at the query result layer by applying a mask function defined in the column schema; the mask is applied transparently to the results returned to the user, and the underlying data remains unchanged in storage. The partial mask function uses a format like 'partial(prefix_chars, "prefix_string", suffix_chars)' to expose a fixed number of leading and trailing characters while replacing the middle with a custom string, which is ideal for PII such as SSNs. A subtle behavior is that DDM does not prevent users from inferring masked data through brute-force queries or side-channel attacks, so it should be combined with other security measures like auditing and encryption for sensitive PII.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
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FAQ
Implement a secure environment — This question tests Implement a secure environment — Read the scenario before looking for a memorised answer..
The correct answer is: Dynamic Data Masking with a partial mask function — Dynamic Data Masking (DDM) with a partial mask function is the correct choice because it allows you to obfuscate sensitive data at query time without altering the underlying storage. For a Social Security number, you can apply a mask like 'partial(0, "XXX-XX-", 4)' to expose only the last four digits to users in the 'CustomerService' role, while the full value remains intact in the database.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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