Oracle窗口函数中的Sum

Question

谁能告诉我在下面的代码片段中，sum在oracle分区的sum (SUM(SUM(VAL)))中的意义是什么？

SELECT NMS,
       SUM(SUM(VAL)) OVER(PARTITION BY NMS),  ---- SIGNIFICANCE
       EMPNO,
       SUM(SUM(VAL)) OVER(PARTITION BY EMPNO)   ---- SIGNIFICANCE
  FROM PART_TEST_PART
 GROUP BY NMS, EMPNO;

Answer 1

它计算每个NMS (对于第一个)和EMPNO (对于第二个)的VAL的总和。

首先计算group by + SUM(VAL)，然后分析根据该结果进行计算。

例如，如果在group by of之后有结果

EMPNO  NMS SUM(VAL)
1      a   15
1      b   24
2      a   50

你会有SUM(SUM(VAL)) OVER(PARTITION BY NMS)作为

EMPNO  NMS SUM(VAL) SUM(SUM(VAL)) OVER(PARTITION BY NMS)
1      a   15       65  (15+50 for NMS = a)
1      b   24       24  (24 for NMS = b)
2      a   50       65  (15+50 for NMS = a)

你会有SUM(SUM(VAL)) OVER(PARTITION BY EMPNO)作为

EMPNO  NMS SUM(VAL) SUM(SUM(VAL)) OVER(PARTITION BY EMPNO)
1      a   15       39  (15+24 for EMPNO = 1)
1      b   24       39  (15+24 for EMPNO = 1)
2      a   50       50  (50 for EMPNO = 2)