SQL-select top 3 values per group WITH CONDITION

Question

I want to pull out top 3 selling products for different product category per tag. Data looks like this:

tag  | product_name | product_category | order_count
tag1 | product1     | category1        | 100
tag1 | product2     | category2        | 80
tag1 | product3     | category2        | 60
tag1 | product4     | category3        | 50
......

I know how to pull out top 3 selling products per tag using ROW_NUMBER(), but it will return product1,product2,product3. I don't want product3 because it belongs to the same category as product2. I want product4 instead. How to do this in SQL server?

Answer 1

First ROW_NUMBER removes duplicate rows per tag and product_category, second ROW_NUMBER selects top 3 selling products per tag

;WITH cte AS
 (SELECT *, ROW_NUMBER() OVER(PARTITION BY tag, product_category ORDER BY order_count DESC) AS rn
  FROM yourtable
  ), cte2 AS
  (SELECT *, ROW_NUMBER() OVER(PARTITION BY tag ORDER BY order_count DESC) AS rn2
   FROM cte
   WHERE rn = 1
   )
   SELECT *
   FROM cte2
   WHERE rn2 <= 3

Demo on SQLFiddle

Next one uses a derived table

;WITH cte AS
 (SELECT t2.tag, t2.product_name, t2.product_category, t2.order_count,
         ROW_NUMBER() OVER(PARTITION BY t2.tag ORDER BY order_count DESC) AS rn
  FROM (SELECT tag, product_category, MAX(order_count) AS maxCount
        FROM yourtable
        GROUP BY tag, product_category
        ) t1 JOIN yourtable t2 ON t1.tag = t2.tag 
          AND t1.product_category = t2.product_category
          AND maxCount = order_count
  )
  SELECT *
  FROM cte
  WHERE rn <= 3

Demo on SQLFiddle