ITPEC FE Subject A April 2025 Question 21

SQL GROUP BY with HAVING — filter grouped results using an aggregate condition.

The query calculates total sales per product and keeps only those with sales ≥ $5,000:

SELECT ProductID, SUM(UnitPrice * Quantity) FROM OrderDetails GROUP BY ProductID HAVING SUM(UnitPrice * Quantity) >= 5000;

• •GROUP BY ProductID — groups rows by product
• •HAVING SUM(...) >= 5000 — filters groups after aggregation
• •GROUP BY must come before HAVING

Why not others:
- (b) HAVING without GROUP BY — aggregate has no grouping target
- (c) HAVING before GROUP BY — wrong clause order (syntax error)
- (d) WHERE with SUM(...) — WHERE cannot use aggregate functions; it filters rows before grouping

Key rule: WHERE filters rows → GROUP BY groups → HAVING filters groups.

AI-generated — may contain errors