ETL Testing Trivia 2 — Questions and Answers
Question 1: What does the acronym 'ETL' stand for in data warehousing?
- Evaluate, Transfer, Load
- Extract, Transform, Load (Correct answer)
- Extract, Transfer, Link
- Encode, Transform, Load
Correct answer: Extract, Transform, Load
ETL stands for Extract, Transform, Load — the three-phase process of moving data from source systems into a data warehouse.
Question 2: Which type of ETL testing verifies that no records are lost or duplicated during the data movement process?
- Schema validation testing
- Data completeness testing (Correct answer)
- Performance testing
- Referential integrity testing
Correct answer: Data completeness testing
Data completeness testing checks that all expected records from the source arrive intact in the target without loss or duplication.
Question 3: In ETL terminology, what is a 'staging area'?
- The final reporting database
- A temporary storage zone between source and target (Correct answer)
- The source system's backup
- A transformation rule repository
Correct answer: A temporary storage zone between source and target
A staging area is an intermediate, temporary storage location where raw extracted data is held before transformations are applied.
Question 4: Which ETL testing technique compares row counts between the source and target to detect data loss?
- Regression testing
- Reconciliation testing (Correct answer)
- Boundary testing
- Smoke testing
Correct answer: Reconciliation testing
Reconciliation testing compares aggregate counts and sums between source and target to confirm no data was lost or added during the ETL process.
Question 5: What is the primary purpose of a 'lookup transformation' in an ETL pipeline?
- To split a data stream into multiple outputs
- To match source data against a reference dataset to enrich or validate records (Correct answer)
- To remove duplicate rows from the dataset
- To convert date formats across time zones
Correct answer: To match source data against a reference dataset to enrich or validate records
A lookup transformation queries a reference table or dataset to find matching rows, enabling data enrichment or validation against known values.
Question 6: When testing ETL, what does 'data lineage' refer to?
- The age of the data in the source system
- The traceable path data follows from source through transformations to target (Correct answer)
- The number of transformation steps applied
- The indexing strategy used in the target warehouse
Correct answer: The traceable path data follows from source through transformations to target
Data lineage documents and tracks the origin, movement, and transformations of data across the entire ETL pipeline.
Question 7: Which scenario best describes an 'incremental load' in ETL?
- Loading all source data from scratch every run
- Loading only new or changed records since the last successful run (Correct answer)
- Loading data in random batches regardless of change status
- Loading only records flagged for deletion
Correct answer: Loading only new or changed records since the last successful run
An incremental load processes only records that are new or modified since the last ETL run, making it more efficient than a full reload.
ETL Testing Trivia 2
What does the acronym 'ETL' stand for in data warehousing?