Groups above a dynamic threshold

Question

Accepted Answer

The scalar subquery in HAVING computes AVG(amount) * 2 = ((200+400+100+150)/4) * 2 = 212.5 * 2 = 425. The outer query groups by customer: Alice total=600, Bob total=250. HAVING keeps groups where total > 425 - only Alice (600) qualifies. Scalar subqueries in HAVING run once and return a single threshold value, exactly like in WHERE.