ETL Developer Lead Interview Questions and Answers

Star schema and snowflake are data modeling techniques used in data warehousing.

• Star schema is a denormalized schema where a central fact table is connected to multiple dimension tables in a star-like structure.

• Snowflake schema is a normalized form of star schema where dimension tables are further normalized into sub-dimension tables.

• Star schema is more suitable for simpler queries and faster performance, while snowflake schema allows for more flexibility and scalability.

• Star...read more

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.

• Normalization involves breaking down a table into smaller tables and defining relationships between them.

• The goal of normalization is to eliminate redundant data and ensure data dependencies make sense.

• There are different normal forms (NF) such as 1NF, 2NF, 3NF, BCNF, and 4NF, each with specific rules to follow.

• For example, 1NF requires that each column in a table mus...read more

I optimize queries by using indexes, avoiding unnecessary joins, and optimizing where clauses.

• Use indexes on columns frequently used in where clauses

• Avoid unnecessary joins by using subqueries or common table expressions

• Optimize where clauses by using appropriate operators and functions

ETL stands for Extract, Transform, Load. It is a process used to extract data from various sources, transform it into a consistent format, and load it into a target database or data warehouse.

• Extract: Involves extracting data from multiple sources such as databases, files, APIs, etc.

• Transform: Involves cleaning, filtering, aggregating, and converting the extracted data into a format suitable for analysis.

• Load: Involves loading the transformed data into a target database or da...read more