ETL Testing ETL Data Extraction Techniques

Question 1

Which extraction method reads only the data that has changed since the last extraction, minimizing load on source systems?

Accepted Answer

Incremental extraction

Answer

Incremental extraction captures only changed or new records since the last ETL run, reducing processing time and source system load.

Question 2

What is a 'delta' in the context of ETL data extraction?

Accepted Answer

The difference or change in data since the last extraction

Answer

A delta represents the subset of records that have been inserted, updated, or deleted since the previous extraction cycle.

Question 3

Which technique uses database log files to capture data changes for ETL extraction?

Accepted Answer

Log-based Change Data Capture (CDC)

Answer

Log-based CDC reads the database transaction logs to capture inserts, updates, and deletes without adding overhead to the source database.

Question 4

When testing ETL extraction, which validation confirms that no source records were dropped during the pull?

Accepted Answer

Row count reconciliation

Answer

Row count reconciliation compares the number of records extracted against the source to ensure completeness.

Question 5

What does 'online extraction' mean in ETL testing?

Accepted Answer

Extracting data directly from a live, active production system

Answer

Online extraction pulls data from an active source system while it is still handling live transactions, requiring careful concurrency management.

ETL Testing - extract, transform, load Practice Test