DEA-C01 Data Store Management Practice Question

Exhibit

Refer to the exhibit.

{
  "Tables": [
    {
      "Name": "sales",
      "Type": "EXTERNAL_TABLE",
      "Parameters": {
        "EXTERNAL": "TRUE",
        "classification": "csv"
      },
      "StorageDescriptor": {
        "Location": "s3://data-lake/sales/",
        "InputFormat": "org.apache.hadoop.mapred.TextInputFormat",
        "OutputFormat": "org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat",
        "SerdeInfo": {
          "SerializationLib": "org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe",
          "Parameters": {
            "field.delim": ","
          }
        }
      }
    }
  ]
}

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?

⚠ Common exam trap

Watch out — 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.

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 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.

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
Athena reads the table's declared S3 location from the Data Catalog; if no objects exist at that prefix, the query scans nothing and returns zero rows. The partition metadata and schema may be valid, but the underlying files must reside at the specified location.
✗
The SerDe library is incorrect for CSV files.
Why it's wrong here
An incorrect SerDe typically produces errors or garbled values, not an empty result set, so it does not match the symptom. OpenCSVSerde is the correct choice for CSV data. A wrong SerDe would be the cause when columns return nulls or parsing exceptions rather than zero rows.
✗
The table format CSV is not supported by Athena.
Why it's wrong here
Athena natively supports CSV through OpenCSVSerde and LazySimpleSerDe, so the format itself cannot cause zero rows. This distractor exploits uncertainty about supported formats. CSV would be the wrong selection only when the underlying data is genuinely another format such as Parquet or JSON.
✗
Athena cannot read tables from the Glue Data Catalog.
Why it's wrong here
Athena queries Glue Data Catalog tables directly through its Hive metastore integration, so this claim is false and cannot explain zero rows. It tempts candidates unfamiliar with the Athena–Glue relationship. Athena would be the wrong tool only for non-catalog sources such as querying DynamoDB items directly.

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

Go deeper

DEA-C01 Data Store Management Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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