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Introduction to ETL Testing Interview Questions and Answers

Hadoop, Data Science, Statistics & others

Now, if you are looking for a job which is related to ETL Testing then you need to prepare for the 2023 ETL Testing Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important ETL Testing Interview Questions and Answers which will help you get success in your interview.

In this 2023 ETL Testing Interview Questions article, we shall present 10 most important and frequently used ETL Testing interview questions. These questions are divided into two parts are as follows:

Part 1 – ETL Testing Interview Questions (Basic)

This first part covers basic ETL Testing Interview Questions and Answers

Q1. What is ETL and explain why ETL testing is required?

ETL is an abbreviation for extract, transform and load. This process is done for the data which is used to analyze and predict the future of any business. Extracting means locating the data and removing from the source file all the data. Transforming is the process of transporting the data to any required file and loading this file to the target system in the format which is requested or applicable. The need for ETL testing arises as we need to keep a track on data which is being transformed from one system to another. We also need to check the efficiency and speed of this entire process. ETL testing ensures that all data that is being implemented is as per the requirements of the client and provides the necessary output.

Q2. What is the surrogate key?

A surrogate key can be said as a unique identifier which can be used for modeling an entity or an object. It can be a unique key whose significance is to be a primary identifier of any object or entity which is not derived from any other database and cannot be used as a primary key. The surrogate key can be a unique sequential number. A surrogate key is not always a primary key and it usually depends on the database. It chooses if the database is current or of a temporal kind. When a database is current it stores the current data and needs to have a one to one relationship in data. When it comes to the temporal database there can be a many to one relationship between the primary and surrogate keys.

Let us move to the next ETL Testing Interview Questions.

Q3. Explain what is partitioning and explain the types of partitions?

Hash Partitioning: In this partitioning, all partitioning keys are grouped among the partitions apply a hash function. It is used to ensure the processed group of rows with the same partitioning key have the same partitions.

Q4. What are the ways of updating a table when SSIS is being used?

Use SQL command

Use a staging table to store stage data

Use cache to store data which uses limited space and requires frequent refresh

Use Scripts to schedule tasks

Make use of full database name for updating MSSQL.

Q5. What is a staging area and what is its purpose?

Data staging is usually a collection of processes which is used to prepare the source system data. This data is then loaded into the data warehouse. Data staging includes the following steps:

Source data extraction and data transformation where data is restructured as per customer requirements. Data transformation includes the process of data cleansing and value transformations. It also involves the process of surrogate key assignments.

Part 2 – ETL Testing Interview Questions (Advanced) Q6. Explain the difference between ETL testing and database testing?

The difference between ETL testing and database testing is as below:

ETL testing usually focuses on business intelligence reporting while database testing involves an integration of data.

The tools that are used for ETL testing are Cognos, QuerySurge, and Informatica while QTP and selenium are used for automation of database testing.

The analysis of data in ETL has a potential impact on data. The normal database testing has architectural implementation impacts

ETL testing has deformalized data while database testing uses normalized data.

Q7. What is a fact? Explain the types of facts?

Non-additive: A measure cannot participate in arithmetic functions by using dimension.

Let us move to the next ETL Testing Interview Questions.

Q8. What is the difference between the surrogate key and primary key?

A Surrogate key is said to have sequentially generated numbers which have no meaning. It is just used so as to identify the rows present uniquely. Primary key, on the other hand, is used to identify rows uniquely. It is visible to users and it can be changed as per requirements.

Q9. Define the term slow changing dimension.

The rows in these data in the dimensions can be either replaced completely without having any track record or a new row can be created or inserted. By using this the slow changes can also be tracked.

Q10. Explain the concept of data purging?

Deleting a piece of data from the data warehouse is known as data purging. This data which is deleted is usually data which has rows with null values or spaces which need clean up. In this process cleaning of this kind of garbage or junk, values are done.