ETL Testing Interview Questions and Answers

Introduction

For the top businesses, ETL is taken as an important component managing the business data and the information perfectly. ETL means Extract, Transform, and Load. All these three components are defined with different objectives and purposes.

• Extract means fetching or reading data from a particular database,
• Transform means converting data to a compatible format to report and analyze well, and
• Load means writing or loading final data to the targeted database.

The major ETL testing operations include:

• ETL tools verify either data is fetched correctly or not.
• It verifies either data is converted correctly as needed by the business requirements.
• It verifies either data is loaded into the targeted database correctly or not without any truncate or data loss.
• It makes sure that data is loaded at perfect time frame to enhance the overall scalability and performance.
• Also, it reports the invalid data and replaces the same with default values.

In brief, ETL tools had the capability to work with large historical data perfectly and they are necessary to carry out the ETL testing. With the huge demand for ETL testing, the major ETL testing operations are used by the experts frequently. So, there are plenty of job options that are also available in the global IT marketplace.

If you have complete knowledge of technical features, ETL tools, and the apps, only then you have the chance of getting hired quickly. For this purpose, you should join the software testing program at JanBask Training to get a deeper understanding of various testing concepts.

In this blog, we will discuss the top 15 ETL testing interview questions and answers that are usually asked during the interviews. The questions and answers are prepared carefully by the JanBaskTraining experts giving training on Software testing tools. With the help of these questions, you would be able to give your best shot during the interview and it will also increase your overall chances of getting hired among other candidates.

Read More: What is Software Testing? What are the Different type of Testing?

Do comment your thoughts and don’t forget to share your experiences. We wish you luck in your next interview!

ETL testing interview questions and answers

ETL testing is a popular trend today with plenty of job opportunities and attractive salary options. Here, we have given a complete list of ETL testing interview questions and answers for freshers and experienced to help the job seekers in the best way. We have taken full care to give precise answers to each of the questions. Let us discuss ETL testing interview questions and answers one by one into next sections.

A. ETL testing interview questions and answers for Freshers

1). What is ETL and explain the three basic steps necessary for the data integration process?

ETL means Extract, Transform, and Load. All these three components are defined with different objective and purposes.

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• Extract means fetching or reading data from a particular database,
• Transform means converting data to a compatible format to report and analyze well, and
• Load means writing or loading final data to the targeted database.

2). How can you compare the ETL testing and the manual testing?

ETL is the automated testing process where you don’t need any technical knowledge other than the software. Also, ETL testing is extremely faster, systematic and assure top results as needed by the businesses.

Manual testing is highly time-consuming where you need technical knowledge to write the test cases and the scripts. It is slow, needs efforts, and highly prone to errors.

3). Explain the major ETL testing operations in detail?

ETL tools verify either data is fetched correctly or not. It verifies either data is converted or loaded correctly at a perfect time frame as needed by the business requirements to enhance the overall scalability and performance.

It verifies either data is loaded into the targeted database correctly or not without any truncate or data loss. Also, it reports the invalid data and replaces the same with default values.

4). Define the major steps included in the ETL testing process?

5). Define Facts in ETL testing and different types of Facts?

Facts are the dimensions that are used to analyze data on different parameters. The three popular facts in ETL testing include- 

6). Do you have any idea about Cubes and OLAP Cubes?

Cubes – These are the data processing units that allow multi-dimensional analysis and each of the units is comprised of fact tables and the dimensions.

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OLAP Cubes –These cubes store voluminous data in the multi-dimensional format that consists of facts and categorized as dimensions.

7). Name few popular ETL bugs?

Source bugs, Calculation bugs, ECP related bugs, load condition bugs and the User-Interface bugs.

8). What are the dimensions?

Dimensions are named as groups or categories to sort the summarized data.

B. ETL interview questions and answers for Experienced

9). How will you define the Staging place in ETL testing?

The Staging place is the temporary storage area that is used during the Data Integration process. Here, Data is analyzed carefully for redundancy and duplication.

10). Define the ETL mapping sheet and its significance?

The ETL mapping sheet contains all necessary information from the source file and stores the details in rows and columns. This mapping sheet helps experts in writing SQL queries to speed up the testing process.

11). What are the tracing level in ETL testing and its types?

Tracing levels define the volume of data stored in the log files. They are divided into two major categories, these are Normal and Verbose. The normal category defines the tracing level in detail while the verbose category defines tracing level at each row.

12). What is Fact Granularity?

The level at which information of Fact is stored is named as Grain of Fact or Fact Granularity.

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13). Explain what is Transformation in ETL testing?

Transformation is defined as the repository objects to generate, modify or pass the data. There may be Active Transformation and Passive Transformation. It may be beneficial in different ways:

• It helps in getting values from tables quickly.
• It has the capability to update slowly changing dimension tables.
• It checks or verifies either record exists or not inside the table.

14). What is the usage of dynamic cache and static cache in transformations?

The dynamic cache is used to update the master table or dimension table that changes slowly. In the case of flat files, the static cache is used.

15). What are the Schema objects and how they are helpful in ETL testing?

The schema objects are the logical structure to define the database data including tables, views, clusters, indexes, database links or function packages, etc.