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When window functions are evaluated
Window functions and GROUP BY
Summary

## Instruction

Great. As you can see, it's fairly simple to create quite advanced statistics very easily thanks to how window functions behave with GROUP BY. Let's take a look at other use cases.

For instance, we may make a ranking based on an aggregate function. Take a look:

SELECT
country,
COUNT(id),
RANK() OVER(ORDER BY COUNT(id) DESC)
FROM auction
GROUP BY country;

We grouped auctions with respect to the country, counted the number of auctions from each country... and then we created a ranking based on that count of auctions.

## Exercise

Now, group the auctions based on the category. Show category_id, the sum of final prices for auctions from this category and a ranking based on that sum, with the highest sum coming first.

### Stuck? Here's a hint!

Use

RANK() OVER(ORDER BY SUM(final_price) DESC)
as your window function.