19.1 C
Wednesday, November 29, 2023
Home > Interview TipsETL Testing Interview Questions and answers

ETL Testing Interview Questions and answers

Among lakhs and lakhs of IT students who graduate in a year, every single graduate will be qualified to bag the Software Tester or ETL Tester job. So all we have to concentrate on is how to stand unique from others to grab the employer’s attention. 

Most of the candidates could explain the entire concept of Software Testing. But, they may lack the practical experience of choosing the apt and optimized technique to solve the problem while testing Big Data files. Therefore, this article can guide the candidates on a tour of possible and most frequent ETL Testing Interview Questions. 

General Questions:

Concentrating on ETL Testing Interview Questions is necessary to handle the technical part of the interview. Though these technical skills matter most in an interview, one can’t deny that soft skills like presentation, communication, and other analytical skills leave a good impression on recruiters. Here are a few general questions and answers that match any interviews. 

  1. Tell us about yourself?
  2. What are your strengths and weaknesses?
  3. Who is your inspiration?
  4. Tell us about the experience about when and how you overcome your weakness?

In addition to the ETL Testing Interview Questions, going through these general questions will take you nearer to the job you desire.

Points to be noted before answering these introduction questions:

  • Don’t detail your personal information that is irrelevant to this interview.
  • Make sure the strength you mention is positive for the job role.
  • Don’t be self-boasting.

ELT Testing:

Nowadays, Software testers are equally in demand with software developers. Expert ELT testers are hired in large numbers to handle data of high volumes and diverse types. Here is our effort to address those technical experts who are not exposed to ETL Testing Interview Questions in their careers. After professional research on “ETL Testing Interview Questions” across various websites, blogs and books, we finalized the Top 25 ETL Testing Interview Questions with crystal clear answers. 

Tips for facing Software Testing Interview:

  • The prior requirement to crack any interview is to possess enough technical knowledge.
  • Have a deep knowledge of traditional manual testing skills to Automated Testing, ELT Testing and other related concepts.
  • Then refer to multiple sources to practice possible ETL Testing Interview Questions.
  • ETL Testing involves Big Data and Data warehousing concepts. So, learn these and practice the possible ETL Testing Interview Questions on these technologies.

All these are enough to gather sufficient knowledge about ETL Testing. But, these aren’t enough to crack the interview. The fresher’s who are new to this Testing industry might not have faced ETL Testing Interview Questions. Therefore, this “Top 25 ETL Testing Interview Questions” article is highly recommendable for any candidate who is keen on experiencing the interview style ETL Testing Interview Questions.

Questions and answers specific to ELT Testing:

Before looking at these questions, let’s figure out the possible concepts from which candidates can expect their ETL Testing Interview Questions. Big Data, Business Intelligence, Data warehousing Techniques and SQL are the major components of ETL Testing.

ETL Testing Interview Questions related to Big Data:

Under this category, we could find questions related to Big Data, Data warehousing and Business Intelligence.

1. How do ETL Testing and Business Intelligence complement each other?

The ETL Testing assists Business Intelligence in converting unstructured Big Data from various possible sources. The major contribution of ETL testing in BI is removing the noisy data and converting it into standard data with necessary test cases and constraints. 

In turn, Business Intelligence Tools comes as handy assistance to analyse and predict the commercial reach and value with modern Business Intelligence Tools to enhance the business. 

2. What is a Data warehouse?

The data warehouse is similar to a storage space where the large-scaled businesses store their integrated data and information from widespread sources and aggregate them into single central storage which allows retrieving, modifying or displaying the data through suitable schematic queries whenever needed. 

3. What are the techniques used in Data warehouse testing? 

The data warehouse testing comprises two techniques to transfer the data from the source to the storage location. They are ELT Testing and Business Intelligence.

ELT TestingBusiness Intelligence
ELT Testing concentrates on the process of extracting, transforming and loading the data.BI techniques are used to convert the stored data into reports or insights to the users using BI tools.
This ELT Testing is responsible for the process from the source file to the Data warehouse.This Business Intelligence is responsible for processing the stored data of the data warehouse to the dashboards.

ETL Testing Interview Questions specific to the testing process:

Under this category, one can come across the possible testing types, test cases, and bugs during the ETL testing. In short, these are the highly expectable ETL Testing Interview questions that may be posed to check the depth of a candidate’s knowledge on ETL Testing.

4. What is your experience with ETL Testing?

We worked on a Business Intelligence project where we dealt with the data of a Shopping complex. We processed the structured and unstructured data of the various fields and converted them into a standard schema. In this process, we employed ETL testing to successfully transform data from the source file to the destination by creating necessary test cases like Null Value, Data Validation, and a few more.

5. Where ELT Testing is used and why?

Business Intelligence is a technique of using profound data as an asset to analyse the needs of the people and develop the business. ETL Testing is best suited for Business Intelligence because they undergo extracts, transforms and load operations in an efficient sequential order.  Before storing the data to the destination, it converts the data of various types into a suitable form that fits in the warehouse and cleanses the data, omitting the unwanted data and fixing the bugs. This eases the task of BI tools of presenting the data to the end-user with the already processed data in the warehouse. 

6. What is ETL Testing?

Extract, Transform and Load is the order of the process in RTL Testing. As the name implies, this is the process of extracting the data from OLTP databases, transforming the data to adapt to the data warehouse framework and loading the data into data marts. 

For example, the data collected from various sources may be text, spreadsheet, multimedia files. Integrating these data and loading them into the data warehouse after the cleaning process is the main process carried out by ETL.

7. Explain the phases of ETL?

ETL Testing process undergoes 5 phases.

  • Requirement Analysis: Requirement Analysis is understanding the business needs and examining the necessary elements to undergo the project.
  • Test Planning: Acquiring data from the sources and devising a plan to perform the testing process.
  • Designing: This phase designs suitable business models and develops test cases to execute the testing.
  • Test Execution: This phase executes the testing with the help of the pre-processed data. They clean the bugs and convert the data as a suitable one for the framework.
  • Populate data: After performing the necessary calculations and testing, the results are derived from the output. This phase is responsible for such data populating tasks.
  • Build reports: This phase generates reports, insights and graphs to present in dashboards or other means for people’s easy reference.

8. Mention a few ETL Testing types?

Types of ELT Testing Functions
GUI / Navigation TestingThis type types the Graphical User Interface and the navigations used with the front end summaries.
Source to Target TestingThe correctness of the data values from the source file to the target is tested by this type.

9. Which data test type is suitable for testing the data type length?

The metadata testing type tests the conditions, types, index, length and other constraints of the data.

10. What will be the test case to resolve mistyped values?

The misspelled or mistyped data can be handled by developing a correctness issue test case that checks the wrongly entered values, verifies the NULL, Not Unique and range levels.

11. What are the bugs you faced while working with ETL Testing?

 I have faced a few bugs while working on a testing project with the data of a shopping complex. 

Input/Output Bug:The system will deny the valid inputs and will accept the invalid and wrong values.
Calculation Bug: 


The mathematical calculation will return wrong values resulting in the wrong outputs.

12. Differentiate ETL and ELT Testing?

In simple words, ELT and ETL differ in the order of execution. 

Extract Transform Load (ETL): They extract, transform and then load the data.

Extract Load Transform (ELT):  They extract, load and then transform the data.

13. What are the responsibilities an ETL Tester should possess?

An ETL Tester should possess,

  • Validating data sources
  • Using extraction methods for data transfer
  • Deriving the suitable transformation logic
  • Finally, storing the data into data marts or warehouses.

14. List a few common test cases

Null ValidateChecks the places where the data is not available and verifies the NULL Value in whichever cells it is mentioned.
Duplicate Check 


To check whether any repetition of the records is present. This is done using the primary, foreign keys to remove the duplicate if any.

15. What are the ELT Testing Tools you are familiar with?

  • DataQ
  • Right Data
  • Query Surge

16. What is Data Accuracy testing?

This type checks whether the data transformed is accurate as expected without any change. The transformed data from the source should match the expectations accurately.

17. What is Incremental Testing?

This testing type ensures whether the changes made to the data are in sync with the business model. The insert operation, calculations or delete operations performed on the data is checked for integrity.

18. What is a constraint validation test case?

The conditions designed to function the software should be subjected to constraint validation testing. Writing a condition checking test case to match the specific table is the main process in this case.

19. What are Race condition bugs?

If the system hangs/crashes due to any load or memory issues and restricts the user from running their platforms, this is said to be Race Condition bugs.

20. How will you handle it if the device doesn’t respond to the application?

These are the hardware bugs that may occur in a system. To handle these bugs, updating the applications, rolling back the old versions, re-installing the applications may rectify the bugs.

ETL Testing Interview Questions related to SQL Queries:

Here are a few sample testing interview questions of SQL that include set operators, functions, joins and other functions of SQL.

21. In what way SQL contributes to ETL Testing?

Testers usually fetch data from diverse sources. In this process, the data to be collected from various sources should undergo several joins and set functions which are possible in SQL queries. 

22. What set operators will help in ETL Testing?

  • Union
  • Union All
  • Minus
  • Intersect 

These are the few set operators used in SQL queries.

23. List the aggregate functions?

  • Max
  • Min
  • Sum
  • Count
  • Average

24. Write a query to display the count of employees in a particular department of salary 25000.

SELECT COUNT (*) FROM Employee WHERE Department = ‘CSE’ and Salary = ‘25000’.

25. Write a query to display the different products purchased by the customer.



We hope that this list of top 25 ETL testing interview questions help you in securing your future job in the digital industry.

More resources : Software Tester interview questions25 Functional Testing Interview Question and Answers | Top 10 Software Testing Interview Questions and Answers |Top 10 Automation Testing Interview Questions


- Advertisement -spot_img

More articles

- Advertisement -spot_img

Latest article