- A
The source files are in an incompatible format; convert to CSV
Why wrong: Format is not related to duplicate key errors.
- B
The sink table schema does not match the source; update the schema
Why wrong: Schema mismatch would cause a different error.
- C
The copy activity is not using staging; enable staging
Why wrong: Staging improves performance but does not handle duplicates.
- D
The sink table has a primary key, and the source contains duplicate rows; enable upsert in the copy activity
Upsert behavior can handle duplicate key violations.
Question 609 of 851
DP-203 Develop data processing Practice Question
This DP-203 practice question tests your understanding of develop data processing. 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.
You are using Azure Data Factory to copy data from Azure Blob Storage to Azure SQL Database. The copy operation fails with error 'Cannot insert duplicate key'. What is the most likely cause and solution?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
The sink table has a primary key, and the source contains duplicate rows; enable upsert in the copy activity
The error 'Cannot insert duplicate key' indicates that the sink table in Azure SQL Database has a primary key or unique constraint, and the source data contains rows with duplicate key values. Enabling upsert in the copy activity allows Azure Data Factory to handle duplicates by updating existing rows instead of failing, resolving the conflict.
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.
- ✗
The source files are in an incompatible format; convert to CSV
Why it's wrong here
Format is not related to duplicate key errors.
- ✗
The sink table schema does not match the source; update the schema
Why it's wrong here
Schema mismatch would cause a different error.
- ✗
The copy activity is not using staging; enable staging
Why it's wrong here
Staging improves performance but does not handle duplicates.
- ✓
The sink table has a primary key, and the source contains duplicate rows; enable upsert in the copy activity
Why this is correct
Upsert behavior can handle duplicate key violations.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse duplicate key errors with schema or format issues, or think staging is required for deduplication, but the correct solution is to use upsert to handle primary key conflicts.
Detailed technical explanation
How to think about this question
Azure Data Factory's copy activity uses bulk insert by default, which fails on primary key violations. Enabling upsert (via 'Write behavior' set to 'Upsert') leverages Azure SQL Database's MERGE statement under the hood, allowing the copy activity to insert new rows and update existing ones based on the specified key columns. This is critical when source data may have overlapping keys due to incremental loads or data reconciliation.
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 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.
Visual reference
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
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.
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FAQ
Questions learners often ask
What does this DP-203 question test?
Develop data processing — This question tests Develop data processing — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The sink table has a primary key, and the source contains duplicate rows; enable upsert in the copy activity — The error 'Cannot insert duplicate key' indicates that the sink table in Azure SQL Database has a primary key or unique constraint, and the source data contains rows with duplicate key values. Enabling upsert in the copy activity allows Azure Data Factory to handle duplicates by updating existing rows instead of failing, resolving the conflict.
What should I do if I get this DP-203 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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