#sql

What is the difference between SparkSession and SparkContext in Spark?

Write an SQL query to find the second-highest salary from an employee table.

What are Airflow Operators? Give examples.

Explain the differences between Data Warehouse, Data Lake, and Delta Lake

Explain the differences between a Data Lake and a Data Warehouse.

Can you explain the difference between OLTP and OLAP?

Describe a time when you had to optimize a slow SQL query. What steps did you take?

How do you handle NULL values in SQL? Mention functions like COALESCE and NULLIF.

What is a Common Table Expression (CTE), and when would you use it?

What is the difference between a primary key and a unique key?

What is the difference between WHERE and HAVING clauses in SQL?

How does Spark's Catalyst Optimizer work? Explain its stages.

Explain the concept of Broadcast Join in Spark. When should it be used?

How do you optimize Spark jobs for better performance? Mention at least 5 techniques.

What is the most difficult task you've ever worked on?

What is Snowflake's architecture, and why is it unique?

Retrieve the most recent sale_timestamp for each product (Latest Transaction).

What is the difference between OLTP and OLAP?

What is the difference between SQL and NoSQL databases?

Explain SQL Window Functions with examples.