DP-300 Plan and implement data platform resources Practice Question
You have an Azure SQL Database with sensitive customer data. You need to mask the credit card numbers so that only users with the 'Unmask' permission can see the full number. Non-privileged users should see only the last four digits. Which feature should you implement?
⚠ Common exam trap
Test-takers frequently confuse Dynamic Data Masking with Always Encrypted, thinking encryption is required for masking, but DDM is purely a presentation-layer obfuscation that does not encrypt the underlying data.
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
✓
Dynamic Data Masking
Dynamic Data Masking (DDM) is the correct feature because it allows you to obfuscate sensitive data in query results without changing the underlying database. You can define a mask on the credit card column that shows only the last four digits by default, and grant the UNMASK permission to privileged users so they see the full value. This directly meets the requirement of role-based partial masking without altering the stored data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Column-level security
Why it's wrong here
Column-level security uses GRANT and DENY on columns to block access entirely, not to substitute masked values; it cannot show only the last four digits. It is tempting because it also targets individual columns, and would be correct when certain columns must be hidden from a role rather than partially displayed.
- ✗
Row-level security
Why it's wrong here
Row-level security filters which rows a predicate returns, leaving column values intact, so credit card numbers would still appear in full. It is tempting because it also restricts data by user, and is correct when users must see only their own rows rather than a masked column value.
- ✓
Dynamic Data Masking
Why this is correct
Dynamic Data Masking applies a masking rule at query time, returning only the last four digits to users lacking UNMASK permission while privileged users see full values. This directly meets the requirement without altering stored data or requiring application changes.
- ✗
Always Encrypted
Why it's wrong here
Always Encrypted encrypts column data so clients decrypt it; authorised users see the full number and unauthorised users see ciphertext, not last-four masking. It is tempting because it protects sensitive columns, and is correct when data must stay encrypted at rest and in transit, including from the database engine.
Go deeper
Related to this question
Learn chapter
Overview of Azure Data Platform Options
Key term
Azure SQL Performance Tuning
Azure SQL Performance Tuning is the process of optimizing the speed and efficiency of queries and database operations in Microsoft Azure SQL Database or SQL Managed Instance to reduce latency and improve throughput.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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