在oracle開發過程中經常會遇到累加、減、乘、除的問題。
下面對這個做個小的總結
--建立測試表
create table aspen(parent_id number,part_id number,qnty number);
insert into aspen values(1,1,2);
insert into aspen values(1,2,3);
insert into aspen values(1,3,2);
insert into aspen values(1,4,5);
insert into aspen values(2,2,3);
insert into aspen values(2,3,5);
insert into aspen values(2,4,7);
--實現累加
select parent_id,part_id,qnty,
sum(qnty) over(partition by parent_id order by part_id) running_prod
from aspen
parent_id part_id qnty running_prod
---------- ---------- ---------- ------------
1 1 2 2
1 2 3 5
1 3 2 7
1 4 5 12
2 2 3 3
2 3 5 8
2 4 7 15
--實現累減
select parent_id,part_id,qnty,
sum(decode(rn,1,qnty,-qnty)) over(partition by parent_id order by part_id) running_prod
from (select parent_id,part_id,qnty,
row_number() over(partition by parent_id order by part_id) rn
from aspen)
parent_id part_id qnty running_prod
---------- ---------- ---------- ------------
1 1 2 2
1 2 3 -1
1 3 2 -3
1 4 5 -8
2 2 3 3
2 3 5 -2
2 4 7 -9
--實現累乘
select parent_id,part_id,
exp(sum(ln(qnty)) over(partition by parent_id order by part_id)) running_prod
from aspen
parent_id part_id running_prod
--------- ---------- ------------
1 1 2
1 2 6
1 3 12
1 4 60
2 2 3
2 3 15
2 4 105
--實現累除
select parent_id,part_id,
exp(sum(decode(rn,1,ln(qnty),-ln(qnty))) over(partition by parent_id order by part_id)) running_prod
from (select parent_id,part_id,qnty,
row_number() over(partition by parent_id order by part_id) rn
from aspen )
parent_id part_id running_prod
---------- ---------- ------------
1 1 2
1 2 .666666667
1 3 .333333333
1 4 .066666667
2 2 3
2 3 .6
2 4 .085714286
累乘和累除的缺陷是不能對負數進行運算 因為ln(負數)沒有意義
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