The answer is that the data files are not in the specified S3 location. When an AWS Glue table is defined in the Data Catalog, its metadata points to a specific S3 bucket and prefix; Athena uses this exact path to scan for data. If the actual Parquet, CSV, or JSON files are missing, stored in a different subfolder, or have mismatched file extensions, Athena finds nothing to read and returns zero rows—even though the table schema appears correct. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how Athena and Glue decouple metadata from storage; a common trap is assuming the table definition alone guarantees data exists. Remember the “path mismatch” pitfall: always verify the S3 location in the Glue table properties against where your files actually reside. A quick memory tip: “No files, no rows—check the path before you troubleshoot the query.”
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. 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 sees this AWS Glue table definition in the Data Catalog. The engineer wants to query this table with Amazon Athena, but the query returns zero rows. What is the MOST likely cause?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The data files are not in the specified S3 location.
The most likely cause is that the data files are not in the specified S3 location. When an AWS Glue table is defined in the Data Catalog, Athena reads the table's metadata (including the S3 location) and then attempts to read the underlying data files from that exact path. If the files are missing, misnamed, or in a different prefix, Athena returns zero rows because there is no data to scan. This is a common misconfiguration when the S3 path in the table definition does not match the actual data storage.
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 data files are not in the specified S3 location.
Why this is correct
If no files exist at s3://data-lake/sales/, query returns zero rows.
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.
✗
The SerDe library is incorrect for CSV files.
Why it's wrong here
LazySimpleSerDe works with CSV.
✗
The table format CSV is not supported by Athena.
Why it's wrong here
Athena supports CSV.
✗
Athena cannot read tables from the Glue Data Catalog.
Why it's wrong here
Athena integrates with Glue Data Catalog.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the issue is with the SerDe or format compatibility, but the most common real-world cause is simply that the data files are not present at the specified S3 location, leading to zero rows returned.
Detailed technical explanation
How to think about this question
Under the hood, Athena uses the Glue Data Catalog as its metastore; when you run a query, Athena retrieves the table's SerDe, column definitions, and S3 location from the catalog. If the S3 location points to a prefix that exists but contains no objects (or only objects with a different prefix), Athena will return zero rows because the scan finds no data files. A subtle behavior is that Athena does not validate the existence of files at table creation time; it only checks during query execution, so a table can be created successfully even if the S3 path is empty.
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 Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The data files are not in the specified S3 location. — The most likely cause is that the data files are not in the specified S3 location. When an AWS Glue table is defined in the Data Catalog, Athena reads the table's metadata (including the S3 location) and then attempts to read the underlying data files from that exact path. If the files are missing, misnamed, or in a different prefix, Athena returns zero rows because there is no data to scan. This is a common misconfiguration when the S3 path in the table definition does not match the actual data storage.
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: "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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