Top 3 cities by revenue

Question

A city-operations review opens with the three biggest revenue markets, strongest first.

From `city_sales`, return `city` and `total_revenue`, restricted to the top 3 cities by revenue and ordered from highest to lowest. **Row order matters for this question.**

Accepted Answer

Step 1: Aggregate transactions to city level with `GROUP BY city` and `SUM(revenue)`. Step 2: Sort the aggregated rows with `ORDER BY total_revenue DESC`. Postgres allows referencing the alias in `ORDER BY` because it runs after the `SELECT` list is projected. Step 3: Cut the list with `LIMIT 3`. `LIMIT` is applied after sorting, so it genuinely gives the top three. Step 4: Keep the `ORDER BY` in the final query — the result is a ranked list, so row order is part of the answer.

Top 3 cities by revenue

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