Ernst & Young Data Engineer Interview Questions and Answers

Star schema has a single fact table connected to multiple dimension tables, while Snowflake schema has normalized dimension tables.

• Star schema denormalizes data for faster query performance

• Snowflake schema normalizes data to reduce redundancy

• Star schema is easier to understand and query

• Snowflake schema is more flexible and scalable

• Example: A star schema for a sales database would have a fact table for sales transactions connected to dimension tables for products, customers, a...read more

Transient tables are temporary tables, fact tables contain quantitative data, and dimension tables contain descriptive data.

• Transient tables are temporary and used for intermediate processing or storing temporary data.

• Fact tables contain quantitative data such as sales, revenue, or quantities.

• Dimension tables contain descriptive data like customer names, product categories, or dates.

Use SQL query to find the maximum salary for each department

• Use GROUP BY clause to group the data by department

• Use MAX() function to find the maximum salary within each group

• Join the tables if necessary to get department information

SQL order of execution determines the sequence in which different clauses are processed in a query.

• SQL query is parsed and validated first

• Next, the query optimizer creates an execution plan

• Execution plan includes steps like table scans, index scans, joins, etc.

• Finally, the query is executed and results are returned

List and tuple are both sequence data types in Python, but the main difference is that lists are mutable while tuples are immutable.

• Lists are enclosed in square brackets [], while tuples are enclosed in parentheses ().

• Lists can be modified by adding, removing, or changing elements, while tuples cannot be modified once created.

• Lists are typically used for collections of similar items, while tuples are used for heterogeneous data or to represent a fixed set of values.

• Lists have...read more