Students often search for "Accenture ETL testing interview questions", "Cognizant ETL testing interview questions" or "Capgemini ETL testing interview questions". Large IT service companies hire many ETL testers for client projects, and their interviews focus on the same practical skills.
Read This First
What ETL Testing Projects at Service Companies Look Like
- Clients: often banking, insurance, healthcare, retail and telecom companies in the US, UK and Europe.
- Tools: SQL with Oracle, SQL Server, Teradata, Snowflake or Redshift; ETL tools like Informatica, DataStage, SSIS, Azure Data Factory or AWS Glue; Jira or ALM for defects.
- Work style: mapping documents from the client, test cases and execution in SIT and UAT cycles, daily status calls, often agile sprints.
Typical Interview Rounds
| Round | Freshers | Experienced |
|---|---|---|
| Online assessment | Aptitude, reasoning, basic SQL or coding | Sometimes a SQL or technical MCQ test |
| Technical 1 | SQL, DBMS, ETL basics | SQL, ETL testing process, project deep-dive |
| Technical 2 / client | — | Scenarios, tools on the project, sometimes client interview |
| HR / managerial | Relocation, shifts, bond policies | Notice period, expectations, team fit |
ETL Testing Technical Questions (Q1–Q12)
1. Explain the ETL testing process you followed.
Requirement and mapping review, test plan, test cases, test data, execution with SQL, defect logging, retest, regression and sign-off. See ETL testing process.
2. What types of ETL testing have you done?
Count and completeness, transformation, data quality, metadata, referential integrity, incremental and regression testing.
3. How do you test an incremental load?
Insert and update source rows, run the load, and confirm only changes were applied, with no duplicates on re-run.
4. What is SCD Type 2 and how do you test it?
History by new rows with dates or a current flag; test one current row per key, correct expiry and no gaps. SCD testing.
5. What is a mapping document?
The source-to-target specification with column mappings and transformation rules.
6. What is the difference between SIT and UAT for ETL?
SIT is the testing team validating the integrated pipeline; UAT is business users confirming the data meets their needs.
7. What is a fact and a dimension?
Facts hold measures; dimensions hold descriptive context. Details.
8. How do you test data in a report?
Recreate report figures with SQL on the warehouse and compare.
9. What do you check in a session or job log?
Rows read, written and rejected, errors and run time, reconciled against your SQL counts.
10. How do you handle rejected records?
Verify source = target + rejects and that each reject reason matches the mapping rules.
11. What is regression testing in ETL?
Re-running existing checks after changes to ensure nothing else broke, ideally automated.
12. Which defect tracking tool have you used?
Answer honestly, for example Jira or ALM, and describe your defect lifecycle.
SQL Questions (Q13–Q18)
13. Find records in source not in target.
EXCEPT or MINUS on keys, or LEFT JOIN target WHERE target key IS NULL.
14. Find duplicates.
GROUP BY key HAVING COUNT(*) > 1.
15. Second highest salary.
MAX below the MAX, or DENSE_RANK() = 2.
16. Delete duplicate rows keeping one.
Use ROW_NUMBER() partitioned by the key and delete rows with number > 1 (syntax depends on the database).
17. Difference between UNION and UNION ALL.
UNION removes duplicates; UNION ALL keeps them.
18. Write a query to compare totals by month.
GROUP BY month on both sides with SUM, then compare with EXCEPT or a join.
More SQL: SQL queries for ETL testing interviews.
Project and Scenario Questions (Q19–Q25)
19. Explain your current project.
Client domain, sources, target warehouse, your role, number of tables, tools and one achievement. Freshers: an honest practice project. Project ideas.
20. Tell me about a critical defect you found.
Rule, query, impact, root cause, fix. Defect examples.
21. Source and target counts differ. What do you do?
Check filters, rejects, duplicates and late data, find the exact keys and log a defect with evidence.
22. The developer says your defect is not a defect. What do you do?
Refer to the mapping document, show the query and sample data, and involve the business analyst if the rule is unclear.
23. How do you prioritise when time is short?
Test critical tables and financial fields first, automate repeat checks, and report risks clearly.
24. Have you automated any ETL tests?
Describe any SQL scripts, Python or tool-based automation honestly. ETL automation.
25. How do you work with an onsite or client team?
Daily status updates, clear defect reports, overlap hours for calls and documented clarifications.
Preparation Plan
- SQL daily: joins, GROUP BY, EXCEPT/MINUS, window functions.
- Revise ETL and data warehouse concepts: ETL testing notes.
- Prepare a 2-minute project explanation and two defect stories.
- Take the free mock test.
- Freshers: also prepare aptitude and the fresher questions.
Prepare for your ETL testing interview: top 50 questions · in-depth answers · for experienced (3–5 years) · for 10 years experience · SQL query questions · scenario-based questions · data warehouse questions · questions for freshers · free mock test · database testing questions · Python ETL testing questions · Informatica questions · SQL questions for freshers · DBMS questions · data validation questions
More guides for Indian students: ETL full form · ETL testing with example · ETL testing jobs in India · ETL testing course in India · ETL training in Hyderabad, Bangalore & Pune · best ETL testing course on Udemy · ETL testing roadmap · ETL tester vs ETL developer · interview questions for freshers · free ETL testing mock test · SQL for testers · QA to data engineer · ETL testing kya hai (Hindi) · ETL testing projects for practice · ETL testing notes · work from home ETL jobs
Frequently Asked Questions
What ETL testing questions are asked at large IT service companies?
Mostly the ETL testing process, testing types, incremental loads, SCDs, mapping documents, SQL queries, project explanation and defect scenarios.
Are these official Accenture, Cognizant or Capgemini interview questions?
No. They are commonly reported topics for ETL testing roles at large service companies. Each company's process varies, so check official careers pages.
Is SQL important for ETL testing interviews at service companies?
Yes. SQL is tested in almost every technical round for ETL testing roles.
How should freshers prepare for service-company ETL testing interviews?
Prepare aptitude for the online test, SQL and DBMS basics, ETL concepts and one honest practice project.
Do service companies ask about Informatica?
Often, when the project uses it. Know the basics and be honest about your experience.
Asim Noaman Lodhi
Certified Google Partner · QA Consultant · 12+ Years IT
QA consultant specializing in ETL testing and data quality. Trained 913+ students to transition into data testing roles through hands-on, real-world instruction.