POSTGRESQL DATABASE INTERVIEW QUESTIONS

What is the purpose of the GROUP BY clause in PostgreSQL?

Can you explain how GROUP BY works with an aggregate function in PostgreSQL?

What happens if you use GROUP BY without an aggregate function in PostgreSQL?

How can you use the HAVING clause with GROUP BY in PostgreSQL?

Explain the difference between the WHERE and HAVING clauses in PostgreSQL.

Can you group by multiple columns in PostgreSQL? If yes, how does it work?

How does PostgreSQL handle NULL values in the GROUP BY clause?

What are the performance implications of using GROUP BY in PostgreSQL, and how can you optimize it?

Describe a scenario where GROUP BY can be used with a subquery in PostgreSQL.

Compare the usage of GROUP BY in PostgreSQL and ORACLE SQL. Highlight any key differences or similarities.