7. Grouping & Filtering

This module teaches you how to summarize datasets and filter aggregate results without breaking query correctness.

Lessons

• GROUP BY
• HAVING Clause
• GROUP BY with ROLLUP

Decision Guide

Goal	Clause to use	Why
Group rows by one or more keys	GROUP BY	Produces aggregate result sets
Filter rows before grouping	WHERE	Reduces rows early for better performance
Filter grouped results	HAVING	Evaluates conditions after aggregation
Add subtotal and grand total rows	WITH ROLLUP	Generates reporting-friendly totals

What's Next

• Continue to 8. Advanced SQL Features