Price spread across shelf categories

A category manager wants to see how wide the price range is in each aisle before planning a pricing review.

From shelf_prices, return for every category: item_count, min_price, max_price, avg_price (rounded to 2 decimals) and price_range (maximum minus minimum). Show the category with the widest range first and break ties alphabetically by category.

1. Step 1: Group by `category` so every aggregate is calculated per aisle.
2. Step 2: `MIN`, `MAX`, `AVG` and `COUNT` can all be used in the same `SELECT` list.
3. Step 3: You can compute the range directly as `MAX(price) - MIN(price)`; a column alias cannot be reused inside the same `SELECT`, but it can be used in `ORDER BY`.

SELECT category,
       COUNT(*)              AS item_count,
       MIN(price)            AS min_price,
       MAX(price)            AS max_price,
       ROUND(AVG(price), 2)  AS avg_price,
       MAX(price) - MIN(price) AS price_range
FROM shelf_prices
GROUP BY category
ORDER BY price_range DESC, category;