Crucial Exams

AWS Certified Data Engineer Associate DEA-C01 Practice Question

An Amazon Athena table stores clickstream events as Parquet files in an S3 location partitioned by year, month, and day. A nightly ETL job currently runs the following query and is incurring high scan costs:

SELECT user_id, page, event_time FROM clickstream WHERE event_time BETWEEN date '2023-07-01' AND date '2023-07-31';

How should you rewrite the SQL to scan the least amount of data without changing the table definition?

  • Include an ORDER BY year, month, day clause to ensure the data is read in partition order.

  • Append a LIMIT clause so the statement becomes:

    SELECT user_id, page, event_time FROM clickstream WHERE event_time BETWEEN date '2023-07-01' AND date '2023-07-31' LIMIT 100000;

  • Create a common table expression (CTE) that selects all columns and then filter the CTE on event_time within the main query.

  • Add a filter on the partition columns, for example:

    SELECT user_id, page, event_time FROM clickstream WHERE year = 2023 AND month = 7 AND day BETWEEN 1 AND 31;

AWS Certified Data Engineer Associate DEA-C01
Data Ingestion and Transformation
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