The correct answer is to configure the crawler to 'Create a single schema for each S3 path' and enable 'Merge tables'. This option works because when CSV files contain extra columns beyond the first file’s schema, the crawler must be told to union all schemas found in that S3 path rather than creating separate tables for each variation. Without merging, the crawler would either fail to capture the new columns or produce multiple tables, breaking the single-table expectation. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of schema evolution in Glue crawlers—a common trap is assuming the crawler automatically handles extra columns, but it requires explicit merging. Remember the memory tip: "Merge for missing columns, single path for single table." This ensures the crawler adds new columns as they appear, preserving a unified schema across all CSV files.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 data engineer is ingesting CSV files from an Amazon S3 bucket into a Glue Data Catalog table. The files have headers, but some files have extra columns not present in the first file. The engineer wants the Glue crawler to automatically detect the schema. Which crawler configuration option should be used?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the crawler to 'Create a single schema for each S3 path' and enable 'Merge tables'.
Option B is correct because when CSV files have varying schemas (extra columns), the Glue crawler must be configured to 'Create a single schema for each S3 path' with 'Merge tables' enabled. This configuration instructs the crawler to union the schemas from all files in the S3 path, adding new columns as they appear, rather than creating separate tables for each schema variation.
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.
✗
Configure the crawler to 'Inherit schema from table' and set the table name.
Why it's wrong here
That option is for updating existing tables, not schema inference.
✓
Configure the crawler to 'Create a single schema for each S3 path' and enable 'Merge tables'.
Why this is correct
This merges schemas from all files in the path.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the crawler to 'Create a single schema for each S3 path' without enabling 'Merge tables'.
Why it's wrong here
Only uses the first file's schema.
✗
Configure the crawler to 'Create a single schema for each S3 path' and set 'Each file as a separate table'.
Why it's wrong here
Creates multiple tables, not desired.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume 'Merge tables' is about combining multiple tables into one, when in fact it merges schemas from multiple files within the same S3 path into a single table definition.
Detailed technical explanation
How to think about this question
Under the hood, the Glue crawler uses a classifier to infer the schema of each file. When 'Merge tables' is enabled, the crawler compares schemas across files and adds any new columns as nullable fields in the unified table definition. This is particularly useful in streaming or evolving data lakes where schema drift is common, as it avoids manual schema 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.
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.
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the crawler to 'Create a single schema for each S3 path' and enable 'Merge tables'. — Option B is correct because when CSV files have varying schemas (extra columns), the Glue crawler must be configured to 'Create a single schema for each S3 path' with 'Merge tables' enabled. This configuration instructs the crawler to union the schemas from all files in the S3 path, adding new columns as they appear, rather than creating separate tables for each schema variation.
What should I do if I get this DEA-C01 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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