SQL Fundamentals · Aggregation & Grouping · Lesson 17 of 17
Filtering Groups with HAVING
Concept
Filtering Groups with HAVING
WHERE filters rows before grouping; HAVING filters groups after aggregation, which is why COUNT and other aggregates can appear in a HAVING clause but not in WHERE.
- Explain the core idea behind Filtering Groups with HAVING.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Filtering Groups with HAVING. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Write a query that finds ages shared by more than one student, using GROUP BY and HAVING.
Ask about this lesson or your next move. The guide explains the path without taking the work away from you.
Ready for the next lesson?
Mark this lesson complete when you have finished the exercise.
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