由变更记录算出历史每次变更的余额

with data as (
    select '2020-04-15' as day,'收入' as type,'test1' as name,100 as amt, 5000 as bal union all
    select '2020-04-16' as day,'支出' as type,'test1' as name,10  as amt, null as bal union all
    select '2020-04-17' as day,'支出' as type,'test1' as name,20  as amt, null as bal union all
    select '2020-04-15' as day,'收入' as type,'test2' as name,200 as amt, 2000 as bal union all
    select '2020-04-18' as day,'支出' as type,'test2' as name,40  as amt, null as bal
)
select
     t2.day
    ,t2.type
    ,t2.name
    ,t2.amt
    ,t2.amt_flag
    ,sum(t2.amt_flag) over(partition by name order by day ) as amt_new
from (
    select
         t1.*
        ,case when type = '收入' then amt else - amt end as amt_flag
    from (
        select '1900-01-01' as day,'收入' as type, name, bal as amt, null as bal from data where bal is not null
        union all
        select * from data
    ) t1
) t2
;