Question

The HAVING clause is used to filter groups based on which function results?

• A. Mathematical
• B. Aggregate
• C. Window
• D. Recursive

Hint:

Remember:
- WHERE filters raw data rows (no aggregate functions allowed).
- HAVING filters summarized group data (aggregate functions allowed).

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the type of SQL functions whose computed output values are used by the HAVING clause to perform group filtering.

Step 2: Understanding Groups and Filtering in SQL:
- When we run a GROUP BY query, individual rows are compressed into logical categories.
- We cannot filter these categories using raw column values because each category contains multiple rows.
- Instead, we must summarize these rows using Aggregate Functions (e.g., SUM(), AVG(), COUNT(), MIN(), MAX()) which compute a single value for each group.

Step 3: Detailed Explanation:
- The HAVING clause acts specifically as a filter for groups formed by the GROUP BY clause.
- It evaluates conditions based on aggregate calculations (e.g., HAVING COUNT(CustomerID) > 5 or {HAVING AVG(Salary) < 40000}).
- Mathematical functions (like ABS() or ROUND()) operate on individual numbers, not group sets.
- Window functions compute values across rows but do not compress groups, and recursive functions are used for hierarchical queries.
- Therefore, the HAVING clause is explicitly designed to filter groups based on Aggregate function results.

Step 4: Final Answer:
The HAVING clause evaluates aggregate function results to perform group-level filtering.
Hence, option (B) is the correct choice.