Excellent! Let's get started with the new stuff.

In Part 4, you learned ranking functions. These are one place where you can apply PARTITION BY and ORDER BY together.

So far, all the rankings we calculated were performed for all the rows from the query result. With that knowledge, we could have calculated the position of each store in the global network based on their ratings:

SELECT
  Id,
  Country,
  City,
  Rating,
  RANK() OVER(ORDER BY Rating DESC) AS Rank
FROM Store;

Now, we can add PARTITION BY to calculate the positions independently for each country:

SELECT
  Id,
  Country,
  City,
  Rating,
  RANK() OVER(PARTITION BY Country ORDER BY Rating DESC) AS Rank
FROM Store;

In this way, we create a separate ranking for each country. Paris and Frankfurt can both get Rank = 1 because there are separate rankings for France and Germany.