Oracle窗口函数中的求和

Question

谁能告诉我在oracle分区中sum(SUM(SUM(VAL)))里面sum的意义是什么，在下面的代码sn-p中

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VAL 每个NMS（第一个）和EMPNO（第二个）的总和。

首先评估 group by + SUM(VAL)，然后分析计算该结果。

例如如果你在 group by of 之后得到了结果

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

您将拥有SUM(SUM(VAL)) OVER(PARTITION BY NMS)

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)

你会拥有SUM(SUM(VAL)) OVER(PARTITION BY EMPNO)

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)