Question

正在处理某项任务，下面是要问的问题，她已指示我们使用CTE

编写用于查询数据库表的SQL查询代码，并编写一个查询，该查询从“ AdventureWorksDW2016CTP3”数据库中的“ FactFinance”中检索财务金额，并按月组织并显示3个月的滚动平均值来返回这些金额。 >

SELECT DateKey,
  month(date) as [Month],
  year(date) as [Year],
SUM ( ALL Amount) OVER (PARTITION BY Date ORDER BY Date ASC) AS Amount
FROM FactFinance

SELECT
    YEAR(Date) AS Year,
    MONTH(Date) AS Month,
    SUM(Amount) AS Amount
FROM FactFinance
GROUP BY YEAR(Date), MONTH(Date)
ORDER BY Year, Month;


WITH CTE AS (
SELECT 
    DateKey AS Month, 
      AVG(Amount) AS AvgAmt
  from FactFinance
  group by DateKey
  )
  SELECT 
    Month,
    AvgAmt
FROM CTE

GO

oUTPUT for last query需要3个月的滚动平均值

Answer 1

首先，您应该知道正确的答案。假设您拥有所有三个月的数据，那么：

SELECT YEAR(Date) AS Year,
       MONTH(Date) AS Month,
       SUM(Amount) AS Amount,
       AVG(SUM(Amount)) OVER (ORDER BY MIN(DATE)
                              ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) as rolling_3month_avg
FROM FactFinance
GROUP BY YEAR(Date), MONTH(Date)
ORDER BY Year, Month;

如果有人告诉我要使用CTE，我可能会这样做：

WITH unnecessary_cte as (
      SELECT YEAR(Date) AS Year,
             MONTH(Date) AS Month,
             SUM(Amount) AS Amount,
             AVG(SUM(Amount)) OVER (ORDER BY MIN(DATE)
                                    ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) as rolling_3month_avg
      FROM FactFinance
      GROUP BY YEAR(Date), MONTH(Date)
     )
SELECT *
FROM unnecessary_cte
ORDER BY YEAR, MONTH;

但是，我们可以尝试读懂您的指导者的想法，并推测她希望您写这样的东西：

WITH ym as (
      SELECT YEAR(Date) AS Year,
             MONTH(Date) AS Month,
             SUM(Amount) AS Amount
      FROM FactFinance
      GROUP BY YEAR(Date), MONTH(Date)
     )
SELECT ym.*,
       (SELECT AVG(Amount)
        FROM ym ym2
        WHERE 12 * ym2.year + ym2.month
                  BETWEEN 12 * ym.year + ym.month - 2 AND
                          12 * ym.year + ym.month
       ) as rolling_3month_avg
FROM ym
ORDER BY YEAR, MONTH;

CTE Rolling 3 Mo Avg

1 个答案: