转自：https://www.cnblogs.com/sooner/p/8043013.html
在oracle开发过程中经常会遇到累加、减、乘、除的问题。下面对这个做个小的总结
—创建测试表
CREATE TABLE TEST(
PARENT_ID NUMBER,
PART_ID NUMBER,
QUALITY NUMBER);
INSERT INTO TEST VALUES(1,1,2);
INSERT INTO TEST VALUES(1,2,3);
INSERT INTO TEST VALUES(1,3,2);
INSERT INTO TEST VALUES(1,4,5);
INSERT INTO TEST VALUES(2,2,3);
INSERT INTO TEST VALUES(2,3,5);
INSERT INTO TEST VALUES(2,4,7);
一、实现累加
SELECT
T.*,
SUM(T.QUALITY) OVER (PARTITION BY T.PARENT_ID ORDER BY T.PART_ID) RUNNING_QUALITY
FROM
TEST T
二、实现累减
SELECT
T.PARENT_ID,
T.PART_ID,
T.QUALITY,
SUM(DECODE(T.RN,1,T.QUALITY,-T.QUALITY)) OVER(PARTITION BY T.PARENT_ID ORDER BY T.PART_ID) RUNNING_PROD
FROM
(
SELECT
T.*,
ROW_NUMBER() OVER(PARTITION BY T.PARENT_ID ORDER BY T.PART_ID) RN
FROM
TEST T) T
三、实现累乘
SELECT
T.*,
ROUND(EXP(SUM(LN(T.QUALITY)) OVER(PARTITION BY T.PARENT_ID ORDER BY T.PART_ID)),0) RUNNING_PROD
FROM
TEST T
四、实现累除
SELECT
T.PARENT_ID,
T.PART_ID,
T.QUALITY,
EXP(SUM(DECODE(RN,1,LN(T.QUALITY),-LN(T.QUALITY))) OVER(PARTITION BY T.PARENT_ID ORDER BY T.PART_ID)) RUNNING_PROD
FROM
(
SELECT
T.*,
ROW_NUMBER() OVER(PARTITION BY T.PARENT_ID ORDER BY T.PART_ID) RN
FROM
TEST T)T
累乘和累除的缺陷是不能对负数进行运算 因为ln(负数)没有意义
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