ETL or Extract-Transform-Load is the process of Extraction, Transformation, and Loading. In this process, ETL systems serve as the foundation of the data warehouse. The role of any ETL team involves building the back room of a data warehouse. ETL systems extract data from the source systems, implement data quality and consistency standards, confirm data, and deliver data in a presentable format.
The ETL teams need to deliver data effectively to end-user tools, document and protect data lineage, extract data from the source, and assure quality. They also need to maintain consistency across sources, deliver data in a format usable by query tools, clean, conform, add value to data, etc. In this article, we’ll look at some ETL interview questions to help you solidify your interview preparation.
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In this article, we’ll cover:
Here are some ETL interview questions and answers to give you an idea of what to expect:
The ETL system helps by removing mistakes, providing confidence measures in data, correcting missing data, tracking the flow of transnational data for safekeeping, presenting data such that end-user tools can use it, and adjusting data from multiple sources so they can be used together.
The lowest/most atomic level of data stored in the fact table by which we can define the facts is called the grain of fact or Fact Granularity.
Mapping is the flow of data from the source to the destination.
A set of instructions describing the data movement from the source to the destination is called a session. A materialized view simply refers to an aggregate table.
A worklet refers to a set of tasks in ETL. It can refer to any set of tasks in the program.
An ETL Validator is a data testing tool to significantly simplify the testing of the Data Warehouse, Data Integration, and Data Migration projects.
Common ETL test cases include Mapping Doc Validation, Data Quality, Correctness Issues, and Constraint Validation.
Check out these ETL testing interview questions to gauge your preparation level:
Again, on the technical side, see if you can answer these ETL developer interview questions:
Lastly, make sure you can answer these SQL interview questions before your interview:
Q1. What is partitioning in ETL? What are the ETL partition types?
The sub-division of the transactions for enhancing their performance is called partitioning. Round-Robin partition and Hash partition are the two types of partitions in ETL.
Q2. What are the data formats available in the ETL system?
There are various data formats in ETL. They include flat files, XML datasets, dimensional data models, independent DBMS working tables, normalized entity/relationship (E/R) schemas.
Q3. What are some of the most used ETL tools?
Some of the most preferred ETL tools include Oracle Warehouse Builder, SAP Data Services, SAS Data Management, IBM Infosphere Information Server, Elixir Repertoire for Data ETL, Power Center Informatica, SQL Server Integration Services, and Data Migrator IBI.
Q4. What is the 3-tier system in ETL?
The 3-tier system in ETL refers to the data warehouse. Its middle tier gives the end-users securely usable data, and the other two layers are on either side of this middle tier. The other two layers are the end-users and the back-end data storage.
Q5. What are the operations involved in the ETL system?
There are three ETL Operations. The first step is extracting from a source, which can be a transnational system like Microsoft, Oracle, or any relational database server. In the second step, this data is then transformed via data cleansing operations to generate a business roll. Lastly, the data is loaded into the target database.
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