ETL testing process and life cycle
What is ETL?
ETL (Extract-Transform-Load) is the process of loading data from source system to the data warehouse. Data is first extracted from OLTP database and non-OLTP systems, then transformed steadfastly to match the data warehouse schema and finally loaded into the data warehouse database.
What is ETL Testing?
ETL is usually allied with Data Warehousing projects but in reality any kind of bulk data movement from a source to a target is ETL. Need to move application data from one source to another for data integration or data migration purposes is quite normal in big enterprises. ETL testing is a data centric testing process to confirm that data transformation and loading has been on expected lines.
ETL process
1. Extract
• Relevant data extraction is the first and foremost step. Data is extracted from multiple heterogeneous sources.
2. Transform
• Transforming data to Data Warehouse format
• Build keys - A key is nothing but single or multiple data attributes that distinctively identify an entity. Various kinds of keys are primary key, composite key, surrogate key, alternate key, foreign key etc. These keys are owned by data warehouse and it never permits any other entity to assign them.
• Cleansing of data: Next step after extraction is cleaning and conforming of data. Cleaning means identification and fixing of errors. Conforming is resolution of conflicts between incompatible data. This is important to make data usable in an enterprise data warehouse. Also, this system creates meta-data needed to diagnose source system problems and enhances data quality.
3. Load
• Loading data into Data Warehouse
• Build aggregates – This is important to improve performance of end user queries. Creating an aggregate is nothing but summarizing and storing data available in fact table.
Challenges in ETL Testing
ETL Testing requires a data centric testing approach and this differentiates it from application testing. Some of the challenges in ETL Testing are:
• ETL Testing entails comparing of huge volumes of data.
• Often data from heterogeneous data sources needs to be tested.
• Complex SQL queries might be required at times as data is often transformed.
• ETL testing heavily depends on availability of test data with diverse test scenarios.
ETL testing training is in great demand. Sky Infotech provides quality ETL testing training in Noida and is ranked highly among institutes vying for best ETL testing training in Noida tag. This institute is easily accessible from every corner of Delhi/NCR as Noida sector-59 and Noida sector-62 metro stations are in close proximity of this institute.

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