ORACEL12c求和SUM(a+b)与SUM(a)+SUM(b)结果不一致问题

今天在oracle12c数据库遇到的问题，下面重现一下：

1、先创建一个临时表 temp、一个数据表bitest_sum;

-- Create table
create table PEC.BITEST_SUM
(
  yyyymm  VARCHAR2(6),
  factno  VARCHAR2(4),
  dept_no VARCHAR2(4),
  product VARCHAR2(6),
  amt     NUMBER default 0 not null,
  amt_ys  NUMBER default 0 not null
)
tablespace BITBS;
-- Add comments to the table 
comment on table PEC.BITEST_SUM
  is 'SUM结果测试';
-- Create/Recreate indexes 
create index PEC.BITEST_SUM_01 on PEC.BITEST_SUM (YYYYMM, FACTNO, DEPT_NO, PRODUCT)
  tablespace IDX_BI;

2、插入各维度数据到temp

DELETE FROM gt_temp;
INSERT INTO gt_temp
(main_code,
v1
)
SELECT 'A','AA01' FROM dual;

INSERT INTO gt_temp
(main_code,
v1
)
SELECT 'B',DEPT_NO FROM(
select 'BB'||dbms_random.string('x',2) DEPT_NO from dual) CONNECT BY ROWNUM <= 1000;

INSERT INTO gt_temp
(main_code,
v1
)
SELECT 'C', lpad(ROWNUM,6,'0') FROM dual CONNECT BY ROWNUM <=1000;

3、插入维度数据及随机值到结果表 bitest_sum

DECLARE
CURSOR C1 IS
    SELECT v1 FROM pec.gt_temp WHERE main_code='A';
CURSOR C2 IS
    SELECT v1 FROM pec.gt_temp WHERE main_code='B';
CURSOR C3 IS
     SELECT v1 FROM pec.gt_temp WHERE main_code='C';
BEGIN
  FOR R1 IN C1 LOOP
    FOR R2 IN C2 LOOP
      FOR R3 IN C3 LOOP
INSERT INTO BITEST_SUM
SELECT '201605',a.v1,b.v1,c.v1, d.amt1,D.AMT2 FROM
gt_temp a,gt_temp b,gt_temp c,
(SELECT round(dbms_random.value(-10000,99999),2) amt1 ,round(dbms_random.value(-10000,99999),2) amt2 FROM dual) d
WHERE a.main_code='A'  AND A.V1=R1.V1 
    AND B.MAIN_CODE='B'  AND B.V1=R2.V1
    AND C.MAIN_CODE='C'  AND C.V1=R3.V1;
    END LOOP;
   END LOOP;
  END LOOP;
 END;  
COMMIT;

4、检查数据结果

5、对结果数据进行update操作。提交之后再查询：

UPDATE pec.bitest_sum2 SET amt_ys=0 WHERE amt_ys<0 AND product LIKE '000%';

pass：加“group by 1”在sql中数据是对的，金额字段加nvl(amt,0)数据也是对的。

此问题已反馈给ORACLE，后续有结果再补充。