ETL Testing Interview Questions and Answers
Ques 1. What is ETL testing?
ETL (Extract, Transform, Load) testing is a process of verifying the correctness of data transformation and loading from source to target databases.
Example:
An example of ETL testing is validating that data from a CSV file is accurately transformed and loaded into a data warehouse.
Ques 2. Explain the difference between ETL testing and database testing.
ETL testing focuses on the data transformation and loading processes, ensuring data integrity during these processes. Database testing, on the other hand, verifies the correctness of data storage, retrieval, and manipulation within a database.
Example:
In ETL testing, you would check if data is transformed and loaded accurately, while in database testing, you might validate SQL queries and stored procedures.
Ques 3. What is a staging area in ETL?
A staging area in ETL is an intermediate storage area where data is temporarily held during the extraction and transformation processes before being loaded into the target data warehouse.
Example:
Data extracted from source systems is first loaded into the staging area, where it undergoes transformations before being moved to the final data warehouse.
Ques 4. What is data profiling in ETL testing?
Data profiling is the process of analyzing and examining source data to understand its structure, quality, and relationships, helping in designing effective ETL processes.
Example:
Data profiling can involve checking for missing values, identifying data patterns, and assessing data distribution in the source system.
Ques 5. Explain the importance of data cleansing in ETL.
Data cleansing involves identifying and correcting errors or inconsistencies in source data, ensuring the accuracy and reliability of data in the target data warehouse.
Example:
Removing duplicate records and correcting misspelled names in source data are examples of data cleansing activities in ETL.
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