甲骨文：需要計算過去3個月的滾動平均值，我們每月有多次提交

Question

我已經在甲骨文中看到了許多滾動平均值的例子，但是做了我想要的事情。

這是我的原始數據

DATE            SCORE   AREA
----------------------------
01-JUL-14       60      A
01-AUG-14       45      A
01-SEP-14       45      A
02-SEP-14       50      A
01-OCT-14       30      A
02-OCT-14       45      A
03-OCT-14       50      A
01-JUL-14       60      B
01-AUG-14       45      B
01-SEP-14       45      B
02-SEP-14       50      B
01-OCT-14       30      B
02-OCT-14       45      B
03-OCT-14       50      B

這是我的滾動平均值的理想結果

MMYY        AVG     AREA
-------------------------
JUL-14      60      A
AUG-14      52.5    A
SEP-14      50      A
OCT-14      44      A
JUL-14      60      B
AUG-14      52.5    B
SEP-14      50      B
OCT-14      44      B

我需要它的工作方式是，對於每個MMYY，我需要回顧3個月，然后AVG得分。 所以，例如，

對於OCT的A區，在距離10月的最后3個月中，有6項研究，（45 + 45 + 50 + 30 + 45 + 50）/ 6 = 44.1

通常我會像這樣編寫查詢

SELECT
  AREA, 
  TO_CHAR(T.DT,'MMYY') MMYY,
  ROUND(AVG(SCORE)
    OVER (PARTITION BY AREA ORDER BY TO_CHAR(T.DT,'MMYY') ROWS BETWEEN 2 PRECEDING AND CURRENT ROW),1)
    AS AVG 
    FROM T

這將查看過去3個月內的最后3個回合

Answer 1

一種方法是將聚合函數與分析函數混合使用。 平均值的關鍵思想是避免使用avg() ，而是將sum()除以count(*) 。

  SELECT AREA, TO_CHAR(T.DT, 'MMYY') AS MMYY,
         SUM(SCORE) / COUNT(*) as AvgScore,
         SUM(SUM(SCORE)) OVER (PARTITION BY AREA ORDER BY MAX(T.DT) ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) / SUM(COUNT(*)) OVER (PARTITION BY AREA ORDER BY MAX(T.DT) ROWS BETWEEN 2 PRECEDING AND CURRENT ROW)
  FROM t
  GROUP BY AREA, TO_CHAR(T.DT, 'MMYY') ;

請注意order by子句。 如果您的數據跨越多年，則使用MMYY格式會產生問題。 最好使用YYYY-MM等格式數月，因為字母順序與自然順序相同。

Answer 2

您也可以指定范圍，而不僅僅是行。

SELECT
  AREA, 
  TO_CHAR(T.DT,'MMYY') MMYY,
  ROUND(AVG(SCORE)
    OVER (PARTITION BY AREA 
      ORDER BY DT RANGE BETWEEN INTERVAL '3' MONTH PRECEDING AND CURRENT ROW))
    AS AVG 
    FROM T

由於CURRENT ROW是默認值，因此ORDER BY DT RANGE INTERVAL '3' MONTH PRECEDING應該有效。 也許你必須做一些微調，我沒有測試關於每月28/29/30/31天問題的行為。

有關更多詳細信息，請查看Oracle Windowing子句 。

Answer 3

SQL> WITH DATA AS(
  2  SELECT to_date('01-JUL-14','DD-MON-RR')  dt,     60   score,    'A' area FROM dual UNION ALL
  3  SELECT to_date('01-AUG-14','DD-MON-RR')  dt,       45      score,    'A' area FROM dual UNION ALL
  4  SELECT to_date('01-SEP-14','DD-MON-RR')  dt,       45      score,    'A' area FROM dual UNION ALL
  5  SELECT to_date('02-SEP-14','DD-MON-RR')  dt,       50      score,    'A' area FROM dual UNION ALL
  6  SELECT to_date('01-OCT-14','DD-MON-RR')  dt,       30      score,    'A' area FROM dual UNION ALL
  7  SELECT to_date('02-OCT-14','DD-MON-RR')  dt,       45      score,    'A' area FROM dual UNION ALL
  8  SELECT to_date('03-OCT-14','DD-MON-RR')  dt,      50      score,    'A' area FROM dual UNION ALL
  9  SELECT to_date('01-JUL-14','DD-MON-RR')  dt,       60      score,    'B' area FROM dual UNION ALL
 10  SELECT to_date('01-AUG-14','DD-MON-RR')  dt,       45      score,    'B' area FROM dual UNION ALL
 11  SELECT to_date('01-SEP-14','DD-MON-RR')  dt,       45      score,    'B' area FROM dual UNION ALL
 12  SELECT to_date('02-SEP-14','DD-MON-RR')  dt,       50      score,    'B' area FROM dual UNION ALL
 13  SELECT to_date('01-OCT-14','DD-MON-RR')  dt,       30      score,    'B' area FROM dual UNION ALL
 14  SELECT to_date('02-OCT-14','DD-MON-RR')  dt,       45      score,    'B' area FROM dual UNION ALL
 15  SELECT to_date('03-OCT-14','DD-MON-RR')  dt,       50      score,    'B' area FROM dual)
 16  SELECT   TO_CHAR(T.DT, 'MON-RR') AS MMYY,
 17           round(
 18           SUM(SUM(SCORE)) OVER (PARTITION BY AREA ORDER BY MAX(T.DT) ROWS BETWEEN 2 PRECEDING AND CURRENT ROW)/
 19           SUM(COUNT(*)) OVER (PARTITION BY AREA ORDER BY MAX(T.DT) ROWS BETWEEN 2 PRECEDING AND CURRENT ROW),1)
 20           AS avg_score,
 21           AREA
 22    FROM data t
 23    GROUP BY AREA, TO_CHAR(T.DT, 'MON-RR')
 24  /

MMYY    AVG_SCORE A
------ ---------- -
JUL-14         60 A
AUG-14       52.5 A
SEP-14         50 A
OCT-14       44.2 A
JUL-14         60 B
AUG-14       52.5 B
SEP-14         50 B
OCT-14       44.2 B

8 rows selected.

SQL>

從下次開始，我希望您提供create和insert語句，以便我們不必花時間准備test case 。

而且，為什么YY格式？ 你沒見過Y2K bug嗎？ 請使用YYYY格式。