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Top 45 Questions to Ask at an Interview for ETL Testing (With Sample Answers)

Top 45 Questions to Ask at an Interview for ETL Testing (With Sample Answers)

ETL is an acronym that stands for “extract, change, and load.” ETL testing is an important part of business analytics and data warehouses. If you want to be an ETL tester, you should be ready to answer a range of technical and background questions. In this article, we’ll talk about 45 ETL testing interview questions and give you some sample answers to help you prepare.

General questions

When the interview starts, the interviewer will probably ask you a few general questions to find out more about you. Here are some typical interview questions that the interviewer might ask to start the conversation:

  • Tell me about yourself.
  • What are some of your favorite things to do?
  • What do you know about our company?
  • How will your skills help our company?
  • What do you do well?
  • What do you think is the worst thing about you?
  • How do you plan to get better at your weak spot?
  • What’s one of the most important things you’ve done?
  • What do you want to do with your work?
  • What do you want to accomplish in your first three months on the job?
  • Where do you see yourself in five to ten years?
  • Do you have anything to ask about the job?

Questions about ETL testing in the past and now

Most likely, the interviewer will ask you what you’ve done in the past as an ETL tester. The answers you give to these kinds of questions help the interviewer figure out how qualified you are and what you can bring to the company. Some common questions about your experience and background in ETL are:

  • How did you learn about architecture and data warehouses?
  • Can you tell me what you know about data warehousing?
  • Since when have you been testing ETL?
  • At your last job, what were some of the things you had to do?
  • How would your old boss describe you?
  • Do you have any professional certifications?
  • How do you start a new project?
  • Have you ever disagreed with your boss about a project at work? What did you say?
  • Can you tell me about a mistake you made and what you did to fix it?
  • How do you work with other people on a team?
  • Can you tell me about the things you’ve done as a leader?
  • Have you ever had to fix someone else’s mistake at work? What did you do when something bad happened?
  • What was the last project you finished that involved testing ETL?

In-depth questions

During your interview, the person who is hiring you as an ETL tester will probably ask you detailed questions to test your technical skills. You can get ready for your interview by thinking about the following:

  • What do ETL testing and data warehousing have in common?
  • What makes ETL testing different from testing by hand?
  • How is testing ETL different from testing a database?
  • How do you choose the parameters for the test session?
  • How do you set up the environment for testing?
  • How do you use the ETL testing cycle’s three steps?
  • What are some of your favorite tools to use when testing ETL?
  • What does “round-robin partitioning” mean to you? What makes it different from hash partitioning?
  • How do you store data using ETL testing and SQL at the same time?
  • When you test ETL, what do you do with mining and intersect?
  • How can you quickly move a large number of records from the source system to the target system?
  • How do you make sure that the data transformation is right and meets business needs?
  • What do you know about testing for mistakes?

Examples of answers to interview questions about ETL testing

Here are some sample answers to ETL interview questions that you can use to prepare for your own:

What do you think ETL testing is good for?

Since data quality is important to the success of a business, the interviewer will probably want to make sure that you think ETL testing is an important way to make sure that data management is done right. Use examples from your past work to help your organization make sure that data is transferred correctly so that important goals can be met.

Example: “One of the best things about running ETL tests is that this process checks records for missing or truncated data during the load process from the source system to the data warehouse. This makes sure that the data is accurate. At my last job, I found this to be a great way to transfer large amounts of data into target systems quickly and correctly, which made managing client data easier.

What do you think are the most important things an ETL tester does?

This question could be asked by the interviewer to find out what you think your job duties are. Use examples of work you’ve done in the past to show how important your role is in ETL testing and data validation.

Example: “As an ETL tester, some of my most important tasks have been to validate data sources, test extraction methods for accurate data transfer, use transformation logic, and load data into target systems in an efficient way. By following these key steps, I was able to make sure that my company’s data warehouse kept accurate record transfers between the source and target systems.

What do you know about commercial ETL testing tools?

With this question, the interviewer can find out what kinds of testing software and tools you know how to use. In your answer, explain how you used commercial tools at your last job, including what kind of project it was, what its goals were, and how much experience you had.

Example: “I’m familiar with the commercial ETL testing tools Adeptia ETL, Informatica PowerCenter, and DBSoftLab. I’ve only used DBSoftLab and Adeptia ETL in the past. At my last job, I used DBSoftLab to manage large amounts of data uploads quickly and correctly as the company grew. Adeptia ETL is also very helpful because it has a lot of easy-to-use features. But I think Adeptia is better at managing data warehouse processes through self-service.

Why is it a good idea to test ETL in SQL?

The interviewer may ask you this question to see how much you know about commercial testing tools and how to use them in SQL. If the company you used to work for used SQL to manage data and business information, give examples of how your methods worked. If not, tell me how you would do that in a SQL server if you could.

Example: “I move data into the server using SQL Server Integration Services (SSIS), which is part of SQL Server. I can choose how to load data into SQL’s SSIS. For example, I can do bulk loads or loads of a few rows at a time. SQL is great for ETL testing because I can change data records for the target system by switching between the “slowly changing dimension” and the “fastly changing dimension” in the SQL server.

When you’ve done an ETL test, what kinds of problems have you run into?

This question can help the interviewer see how well you can find problems on the job and come up with solutions. During ETL testing, your answer should show that you can look at problems and come up with ways to fix them.

Example: “During an ETL testing session, a number of things can go wrong, such as business information not being sent over as well as it should or data being lost. In my last job, before I started ETL testing, I ran into a few software requirements that weren’t clear, but I was able to figure them out. I fixed this problem by telling my IT manager to do data warehousing with SQL integration. This gave my team a clear plan to follow as they worked.

Can you explain how you bring systems together?

Depending on how the company handles data warehousing, the interviewer may ask how you would handle system integration tasks as an ETL tester for their company. Use examples from your own life to show how you plan, organize, and integrate technical data into tasks that require system integration.

“There are many good ways to connect systems, but for most projects, I use vertical system integration. With vertical integration, I start by figuring out the main term or value, and then I slowly break that value into smaller categories.

In my last job, for example, I had to use system integration to sort client information by location. The first thing I did was set up the top level for each state. Then I programmed the counties of the states as sub-categories, after which I was able to finish integrating the system.

Let’s say the source system has 70 records, but you only want to load five records to the target for each test run. What would you do?

The person interviewing you might want to know how you will handle big test projects with short deadlines. Explain how you deal with large data records, how you load a lot of records into target systems, and how you make sure the transfer is done correctly.

Example: “In my previous job, I did use partial testing with a lot of data records. Most of the time, I use a mapping variable with a filtered transformation to divide the test load into smaller groups. This lets me sort each record correctly and group smaller records together so they can be loaded all at once. I can also make a sequence order, which is helpful for data that needs to stay in a certain order, either going up or down.”

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