Question

假设我有以下代表税收的数据：

SELECT trunc(i*i, 3) tax
  FROM generate_series(1.17, 5) i;

    tax   
 -------- 
   1.368  
   4.708  
  10.048  
  17.388  
 (4 rows)

PostgreSQL中是否有任何不错的方法将mill余数放入下一行，如果当前行是最后一行，则必须保留所有剩余项。

所以，我需要做到以下几点：

    tax   
 -------- 
   1.360  
   4.710  
  10.050  
  17.392  
 (4 rows)

它可以是查询或SQL / PL / pgSQL函数。

Answer 1

下一行和最后一行仅在定义了排序顺序后才有意义。我假设排序顺序是由tax asc定义的。

第一个子查询将行号添加到数据中，而第二个子查询计算行数。下一部分是基于行数增加的递归：

with recursive data as (
    select trunc(i*i, 3) tax, row_number() over (order by i) as rn
    from generate_series(1.17, 5) i
),
count as (
    select count(*)
    from data
),
result as (
    select 
        tax, rn, 
        floor(tax* 100)/100 as new_tax, 
        tax- floor(tax* 100)/100 as remainder
    from data
    where rn = 1
union all
    select 
        d.tax, d.rn, 
        case d.rn 
            when count then d.tax+ r.remainder
            else floor((d.tax+ r.remainder)* 100)/100 end as new_tax, 
        d.tax+ r.remainder- floor((d.tax+ r.remainder)* 100)/100 as remainder
    from data d
    join result r on d.rn = r.rn+ 1
    cross join count
) 
select new_tax as tax
from result
order by rn;

Live demo in rextester.

将除法的其余部分放入下一行

1 个答案: