Question

我正在使用Amazon Redshift查询数据。我想选择在每个季度组中产生最多收入的前4个产品。我使用windows函数计算一个季度内每个产品的收入总和值，然后使用另一个窗口函数来获取每个组中的前4个项目。这是我的代码：

SELECT  es.itemid,es.total_Revenue,es.quarter
FROM (         
      SELECT  SALE_CET.itemid
      --get total revenue per quarter
             ,SUM(SALE_CET.totalseller) OVER
                    (PARTITION BY  SALE_CET.itemid,SALE_CET.quarter) AS total_Revenue
             ,SALE_CET.quarter
      --Rank the data by total revenue within each group 
             ,ROW_NUMBER() OVER
                    (PARTITION BY  SALE_CET.quarter ORDER BY total_Revenue DESC
                    ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ) AS ra
      FROM SALE_CET) es
WHERE es.ra <=4

我知道我们可能无法在order-by子句中使用聚合值。但是，如果我想按季度每个项目的总收入订购记录，我该如何实施呢？

感谢您的帮助。

SALE_CET表是从CTE创建的临时表。 Create table命令将类似于：

WITH SALE_CET (userid,itemid, totalseller,year,month,quarter,dayofyear) AS 
    ( SELECT  userid 
             ,itemid
             ,itemprice*orderqty AS TotalSeller
             ,DATEPART (year, orderdatetime) AS year
             ,DATEPART (month, orderdatetime) AS month
             ,DATEPART (quarter, orderdatetime) AS quarter
             ,DATEPART (dayofyear, orderdatetime) AS dayofyear           
      FROM   sales)

Answer 1

如果您在子查询中按收入降序添加另一个ROW_NUMBER（）或DENSE_RANK（），那么您应该能够按外部查询的顺序访问该值。

如下所示。这是一般的想法。

    SELECT
        *
    FROM
    (
        SELECT 
           itemid, 
           total_Revenue,
           quarter
           ra,
           RevenueByItemThenByQuarter=DENSE_RANK() OVER 
                (PARTITION BY  SALE_CTE2,ietemid,SALE_CET2.quarter ORDER BY SALE_CTE2.total_Revenue DESC
        FROM
        (
            SELECT  SALE_CET.itemid
                  --get total revenue per quarter
                         ,SUM(SALE_CET.totalseller) OVER
                                (PARTITION BY  SALE_CET.itemid,SALE_CET.quarter) AS total_Revenue
                         ,SALE_CET.quarter
                  --Rank the data by total revenue within each group 
                         ,ROW_NUMBER() OVER
                                (PARTITION BY  SALE_CET.quarter ORDER BY total_Revenue DESC
                                ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ) AS ra
                  FROM SALE_CET
        )AS SALE_CET2
    )AS es
    WHERE 
         es.ra <=4
    ORDER BY 
         es.RevenueByItemThenByQuarter

子句

1 个答案: