When you are going to attend the ETL interview, you really get puzzled how to answers the questions that will ask by the interviewer. To make this task easier and flawless, the article has assembled a list of questions where you will find top 10 ELT testing interview questions and answers, which will give you quick way to read and learn these. These have designed in the very precise and influencing way; thereby, the interviewee will able to answer confidently, quick, and impressively.
Since there are many questions related to ETL interview, the following assembled is the best and perfect to go through as these have been asked as of now. Concisely, you must give top-priority to these and read them comprehensively.
Q1. What is ETL and explain why ETL testing is required?
Answer: The term ETL stands for Extract, Transform, and Load. This software is used for data need to analyze and forecast the future of any business. ETL comprises three-term; all have different meanings and functions.
- The term is extracting means seeking the data and elimination of all the data from the source file.
- The term transforming means the process of transferring the data to any specific file along with loading that data to the target system accordingly requested.
- The term loads mean to verify that data is loaded at the stipulated time to enhance the performance and scalability.
Q2. What do you mean by surrogate key?
Answer: The role of the surrogate key is to model any object or entity. It is regarded as the unique key intended to know about the primary identifier of any entity or object that is not derived from other databases. Besides, a surrogate key is not always determined as a primary key, and its’ all relied on the database. Its’ depending upon the situation of the database if it is a current kind, then storage will be given to the current database, and it always has a one to one relationship between the primary and surrogate keys while if it is temporal kind, then there will be many to one relationship between the surrogate key and primary.
Q3: What is partitioning, hash partitioning and round robin partitioning?
With an intention is to improve performance, transactions get subdivided, which is called as Partitioning. It allows Informatica server for establishing of the multitude of links to different sources. There are two types of partitioning:
- Hash partitioning
- Round robin partitioning
Hash partitioning is used to partition keys in favour of group data in the middle of the partitions Informatica server when the hash function is applied. Briefly, it is used to enables the groups of rows with the similar partitioning key in the similar partition required to be secured.
Round-Robin partitioning is used to divide the Informatica data evenly to all partitions. This is used only where the number of rows is similar to the process.
Q4. What is a fact? Explain the types of facts?
Answer: In a multidimensional model, a fact is determined at the central part having all the measures required to be analyzed. There are three types of facts:
- Additive: In additive fact, a measure is used to analyze arithmetic calculations by permitting all or few dimensions.
- Semi-additive: In semi-additive facts, a measure is used to analyze arithmetic calculations by permitting a few dimensions only.
- Non-additive: In non-additive facts, a measure is never involved in arithmetic functions with the help of dimension.
Q5. What is the difference between ETL testing and database testing?
- Database testing is used to focus on the integration of data, while ETL testing basically involves focusing on business intelligence reporting.
- The tools used for database testing are QTP and selenium while QuerySurge, Informatica, Cognos, are tools used in ETL testing.
- Database testing is used normalized data while ETL testing usually have deformalized data.
- During the analysis of data, database testing always has architectural implementation impacts while ETL testing results in a potential impact on data.
Q6. Do you about the staging area?
Answer: The term data sagging is used when there is a need to assemble the processes required to prepare the source system data, which is further loaded or transferred into the data warehouse.
Q7. What is a slow-changing dimension?
Answer: This question is often asked during the interview process, and only a few know about it. The purpose of slow changing dimension means it tends to change very slowly or steadily. It means the data available in this process will alter or amend very slowly as compared to others.
Q8: What are the types of data warehouse applications and also explain the difference between data mining and data warehousing?
Answer: There are three types of data warehouse applications have, such as:
- Data Mining
- Info Processing
- Analytical Processing
The basic difference between data mining and data warehousing is in case of data mining; there is a process of fetching hidden predictive information from the massive databases while data warehousing is used for analytical processing of the data in a steady way. Moreover, data warehousing is used to collect data from a multitude of sources into a single repository.
Q9: What are Cubes and OLAP Cubes?
Cubes are those data processing units included fact tables and dimensions used to provide multi-dimensional analysis. OLAP or Online Analytics Processing used to store massive data in a multi-dimensional form for report purpose.
Q10: What are the ways of updating a table when SSIS is being used?
Answer: When there is a need for uploading tables when SSIS is being used, the following process has been applied:
- First, use SQL command, then do staging table to store stage data
- Afterwards, use cache to store data as it needs less space along with required refresh, then use scripts for scheduling tasks.
- Finally, make sure to use the database name to update MSSQL.
The above-written questions are those who have been asked frequently during the ETL testing interview. If you read and learn these questions carefully, you will definitely influence the interviewer.
All the best!