SQL选择每组WITH CONDITION的前3个值

Question

我想针对每个标签针对不同的产品类别挑选出最畅销的3种产品。数据如下所示：

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

我知道如何使用ROW_NUMBER（）提取每个标签中销售量最高的3种产品，但是它将返回product1，product2，product3。我不想要product3，因为它与product2属于同一类别。我要代替product4。如何在SQL
Server中执行此操作？

Answer 1

第一个ROW_NUMBER删除每个标签和product_category的重复行，第二个ROW_NUMBER选择每个标签的前3个畅销产品

;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

示范 SQLFiddle

下一个使用派生表

;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

示范 SQLFiddle