ETL Testing Interview Questions and Answers

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ETL Testing Interview Questions and Answers

  1. What is ETL testing?

    • Answer: ETL testing is a process of verifying the accuracy, completeness, and consistency of data extracted from source systems, transformed as per business requirements, and loaded into target systems. It ensures data integrity throughout the ETL (Extract, Transform, Load) process.

  2. Explain the different types of ETL testing.

    • Answer: ETL testing encompasses various types, including: Data validation testing (checking data accuracy and completeness), Source-to-target mapping testing (verifying data transformations), Performance testing (assessing ETL process speed and efficiency), Security testing (ensuring data security during ETL), and Recovery testing (testing the system's ability to recover from failures).

  3. What are the key challenges in ETL testing?

    • Answer: Key challenges include: Large volumes of data, Data complexity and variety, Data inconsistencies across sources, Understanding complex transformations, Maintaining data quality throughout the process, Integration with different systems, and Ensuring timely completion.

  4. What are the different approaches to ETL testing?

    • Answer: Approaches include: Top-down testing (testing the entire ETL process), Bottom-up testing (testing individual components), and Incremental testing (testing changes incrementally).

  5. How do you ensure data quality during ETL testing?

    • Answer: Data quality is ensured through data profiling, data cleansing, validation rules, and checks for completeness, accuracy, consistency, and uniqueness.

  6. What are some common ETL testing tools?

    • Answer: Some common tools include Informatica PowerCenter, IBM DataStage, Oracle Data Integrator, Talend Open Studio, and Apache Kafka.

  7. Explain the role of metadata in ETL testing.

    • Answer: Metadata provides crucial information about data sources, transformations, and targets. It helps in understanding the ETL process, tracking data lineage, and verifying data integrity.

  8. What are the different types of data validation techniques used in ETL testing?

    • Answer: Techniques include: Data type validation, Range checks, Null checks, Length checks, Format checks, Cross-field validation, and Data comparison with source and target systems.

  9. How do you handle large datasets during ETL testing?

    • Answer: Techniques include: Sampling, Data partitioning, Using specialized tools for large data handling, and Optimizing ETL processes for performance.

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