用前一行值减去当前行值，得到当前行的余额

Question

我需要通过从前一行的值中减去当前行值来获得balanceAmount 。 预期结果如下。

这是我当前的查询

select 
    pp.*,
    pp.topupAmount - sum(pp.chargeAmount) over (over by pp.ROW_NUM rows unbounded preceding) AS balanceAmount
from 
    (select 
         row_number() over (order by ppc.sortDate) ROW_NUM, ppc.*
     from 
         (select 0 as topupAmount, t1.chargeAmount, t1.sortDate  
          from t1
          union all
          select t2.topupAmount, 0 as chargeAmount, t2.sortDate   
          from t2) as ppc
     ) as pp    
order by 
    pp.ROW_NUM

这是我从上面的查询中得到的

我怎么能做到这一点？

Answer 1

您可以使用窗口函数：

select
    t.*,
    sum(topupAmount - chargeAmount) over(order by row_num) balanceAmount
from mytable t

实际上，通过查看您的查询， row_num似乎是一个生成的列，因此您可能想要：

select
    t.*,
    sum(topupAmount - chargeAmount) over(order by sortDate) balanceAmount
from mytable t

Answer 2

你需要窗口函数：

select t.*, sum(topupAmount - chargeAmount) over (order by sortDate) as balanceAmount
from table t;