如何根据 teradata SQL 中的条件计算带有重置的移动总和? [英] How to calculate moving sum with reset based on condition in teradata SQL?
问题描述
我有这些数据,我想对字段 USAGE_FLAG
求和,但当它降至 0 或移动到新 ID 时重置,保持数据集按 SU_ID
和 <代码>星期代码>:
I have this data and I want to sum the field USAGE_FLAG
but reset when it drops to 0 or moves to a new ID keeping the dataset ordered by SU_ID
and WEEK
:
SU_ID WEEK USAGE_FLAG
100 1 0
100 2 7
100 3 7
100 4 0
101 1 0
101 2 7
101 3 0
101 4 7
102 1 7
102 2 7
102 3 7
102 4 0
所以我想创建这个表:
SU_ID WEEK USAGE_FLAG SUM
100 1 0 0
100 2 7 7
100 3 7 14
100 4 0 0
101 1 0 0
101 2 7 7
101 3 0 0
101 4 7 7
102 1 7 7
102 2 7 14
102 3 7 21
102 4 0 0
我已尝试使用 GROUP BY
的 MSUM()
函数,但它不会保持我想要的上述顺序.它将我不想要的 7 和周数组合在一起.
I have tried the MSUM()
function using GROUP BY
but it won't keep the order I want above. It groups the 7's and the week numbers together which I don't want.
有人知道这是否可行吗?我正在使用 teradata
Anyone know if this is possible to do? I'm using teradata
推荐答案
在标准 SQL 中,可以使用窗口函数完成运行总和:
In standard SQL a running sum can be done using a windowing function:
select su_id,
week,
usage_flag,
sum(usage_flag) over (partition by su_id order by week) as running_sum
from the_table;
我知道 Teradata 支持窗口函数,只是不知道它是否也支持窗口定义中的 order by.
I know Teradata supports windowing functions, I just don't know whether it also supports an order by in the window definition.
重置总和有点复杂.您首先需要创建每次使用标志变为 0 时都会更改的组 ID".以下适用于 PostgreSQL,我不知道这是否也适用于 Teradata:
Resetting the sum is a bit more complicated. You first need to create "group IDs" that change each time the usage_flag goes to 0. The following works in PostgreSQL, I don't know if this works in Teradata as well:
select su_id,
week,
usage_flag,
sum(usage_flag) over (partition by su_id, group_nr order by week) as running_sum
from (
select t1.*,
sum(group_flag) over (partition by su_id order by week) as group_nr
from (
select *,
case
when usage_flag = 0 then 1
else 0
end as group_flag
from the_table
) t1
) t2
order by su_id, week;
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