sql 中月份的累计缺失值

Question

i have input data below

date             amount
01-01-2020         10
01-02-2020         15
01-03-2020         10
01-05-2020         20
01-06-2020         30
01-08-2020         5
01-09-2020         6
01-10-2020         10

select sum(date),over(partition date) from table;

after add the missing month values i need output

output

Date            amount                  cum_sum
01-01-2020         10                     10
01-02-2020         15                     25
01-03-2020         10                     35 
01-04-2020         0                      35
01-05-2020         20                     55
01-06-2020         30                     85
01-07-2020         0                      85
01-08-2020         5                      90
01-09-2020         6                      96
01-10-2020         10                     106

Answer 1

You would typically generate the dates with a recursive query, then use window functions.

You don't tell which database you use. The exact syntax of recursive queries and date artithmetics varies across vendors, but here is what it would look like:

with recursive all_dates (dt, max_dt) as (
    select min(date) dt, max(date) max_dt from mytable
    union all
    select dt + interval '1' day, max_dt from all_dates where dt < max_dt
)
select d.dt, sum(t.amount) over(order by c.dt) amount
from all_dates d
left join mytable t on t.date = d.dt
order by d.dt

Answer 2

You simply want a window function:

select t.*, sum(amount) over (order by date)
from table t