HCL Group ETL Developer Interview Questions and Answers

ETL Developers are responsible for designing, developing, and maintaining ETL processes to extract, transform, and load data from various sources into a data warehouse.

• Designing ETL processes to extract data from multiple sources

• Transforming data to meet business requirements

• Loading data into a data warehouse or other target systems

• Developing and maintaining ETL jobs using tools like Informatica, Talend, or SSIS

SCD Type 1 in IICS involves overwriting existing data with new data without maintaining historical changes.

• In IICS, use the Mapping Designer to create a mapping that loads data from source to target.

• Use a Lookup transformation to check if the record already exists in the target table.

• If the record exists, update the existing record with new data using an Update Strategy transformation.

• If the record does not exist, inse...read more

Loads in Informatica refer to the process of moving data from source to target in a data warehouse.

• Loads involve extracting data from source systems

• Transforming the data as needed

• Loading the data into the target data warehouse or database

• Loads can be full, incremental, or delta depending on the requirements

• Example: Loading customer data from a CRM system into a data warehouse for analysis

Use GROUP BY and HAVING clause to find duplicates in a table.

• Use GROUP BY to group rows with same values together

• Use HAVING COUNT(*) > 1 to filter out duplicates

• Example: SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name HAVING COUNT(*) > 1;

I am an experienced ETL Developer with a strong background in data integration and transformation.

• Over 5 years of experience in ETL development

• Proficient in using tools like Informatica, Talend, and SSIS

• Strong SQL skills for data querying and manipulation

• Experience in designing and implementing data warehouses

• Familiar with data modeling and ETL best practices

SSIS is a Microsoft tool used for ETL processes in data integration and data warehousing.

• SSIS stands for SQL Server Integration Services

• It is used for extracting, transforming, and loading data from various sources to destinations

• SSIS can be used for automating workflows, data cleansing, and data migration tasks

• It provides a visual interface for designing data flow tasks and control flow tasks

• Example: Using SSIS to ext...read more

Lookups are used to retrieve related data from another table based on a common key.

• Lookups are used in ETL processes to enrich data by adding additional information from a reference table.

• They are commonly used to replace codes with corresponding descriptions, such as replacing product IDs with product names.

• Lookups can be performed using SQL joins or lookup transformations in ETL tools like Informatica or Talend.