Interview Questions for an ETL Developer

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The ETL developer creates programs to extract, transfer and load data.
The ETL developer creates programs to extract, transfer and load data. (Image: Hemera Technologies/AbleStock.com/Getty Images)

To effectively interview an ETL developer, you must understand the job. The acronym ETL stands for "extract, transfer and load." This is a process that companies use to extract and store electronic data, and an ETL developer's job is to ensure this is done in an efficient and secure manner. An interview for a person applying for this position should include questions regarding experience, knowledge and proficiency with Internet technology and data systems.

What is Partitioning and How Does it Work?

The question challenges the applicant's knowledge of different options in partitioning data. Partitioning is the process of splitting up information into manageable units to make extracting and transferring easier and more efficient. The applicant should be familiar with the main types of partitions: Horizontal, vertical, passthrough, range, hash and key, list and composite partitioning. This question also gives the job seeker an opportunity to display knowledge in emerging technology, as well as in-depth understanding of established practices. The Power Center Informatica Server is one system that handles the extraction of large amounts of data.

What are the Roles and Responsibilities of an ETL Developer?

You want to know if the person fully understands what his responsibilities when developing new programs to help extract, transfer and load new data. An ETL developer analyzes the data being developed and corrects any problems in the programs. Other responsibilities include developing mappings, unit test mappings with test data, providing support and adjustments to the code when in test mode. When the code moves to initial production, the ETL developer oversees the production to ensure quality and uniformity. If there are any glitches in the system, the ETL developer moves in to analyze the issue.

What is the Purpose of Having a Multidimensional Database?

A multidimensional database, or MDB, has a higher performance output and makes for easier data exploration. The MDB also provides a faster output than other databases. An MDB is not as well-known as an OLAP, or online analytical process. Depending on your candidate's experience and specific discipline, he may or may not be familiar with an MDB, but it is a form of an OLAP.

What is the Third Normal Form?

An extension to this question should be: Give an example of a situation where the tables are not in third normal form, and change it so they are.

The candidate should know that column one is dependent on column two, and column two is dependent on column three. When column three is transitively dependent on column one, you must split it into two tables: Table one and table two. If the candidate cannot answer this question, he may not understand what normal form one or two are, and therefore may not have the knowledge necessary to be an ETL developer.

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