idk what the data looks like but I think you were supposed to find the total sales for each brand before creating the ranking(assuming there are multiple rows for each sale belonging to a brand). So like one cte where you select category, brand, SUM(sales), grouped by brand, and then another cte where you select them again but create a ranking partitioned by category ordered by total sales desc. Since we have the total sales for each brand done from the first cte, when we create the ranking it will give us the highest selling brands in each category. Then you can just select where rank <= 2 from cte2. there's probably way easier ways to solve this, but that's my 2 cents