如何从SQL中的当前行数据中减去前一行数据的总和

Question

我有一个表火鸟，它用3列（星期，日期，金额）调用t1。 我需要根据周列和

对数据进行分组

1. 总和正数（库存）
2. 总和负数（已售出）
3. 从已售出（当前记录）中减去库存（上一记录）

我附上了t1和t2的图片

T1：

week    date    amount
18/06/2016  14/06/2016  94
18/06/2016  15/06/2016  0
18/06/2016  16/06/2016  0
18/06/2016  17/06/2016  0
18/06/2016  18/06/2016  -1
25/06/2016  19/06/2016  -2
25/06/2016  20/06/2016  -1
25/06/2016  21/06/2016  0
25/06/2016  22/06/2016  -1
25/06/2016  23/06/2016  -1
25/06/2016  24/06/2016  -3
25/06/2016  25/06/2016  -1
02/07/2016  26/06/2016  -1
02/07/2016  27/06/2016  -2
02/07/2016  28/06/2016  0
02/07/2016  29/06/2016  1
02/07/2016  30/06/2016  0
02/07/2016  01/07/2016  -1
09/07/2016  03/07/2016  -1
09/07/2016  04/07/2016  -1
09/07/2016  05/07/2016  -2
09/07/2016  06/07/2016  0
09/07/2016  07/07/2016  -2
09/07/2016  08/07/2016  -1
09/07/2016  09/07/2016  -3

T2：

week      sold     stock
          null      94
18/06/2016  1       93
25/06/2016  9       84
02/07/2016  3       81
09/07/2016  9       72

我正在使用Firebird，我的最终脚本应该在firebird或标准sql中运行 感谢

Answer 1

基本查询似乎是：

select week, sum(case when amount > 0 then amount else 0 end) as stock,
       sum(case when amount < 0 then amount else 0 end) as sold
from t1
group by week;

Firebird不支持窗口函数，但您也可以使用相关子查询。 CTE有帮助。我认为是：

with t as (
      select week, sum(case when amount > 0 then amount else 0 end) as stock,
             sum(case when amount < 0 then amount else 0 end) as sold
      from t1
      group by week
     )
select t.*,
       (select sum(t2.stock) + sum(t2.sold)
        from t t2
        where t2.week <= t.week
       ) as stock
from t;

编辑：

使用窗口功能（在Firebird 3中），这更容易：

select week, sum(case when amount > 0 then amount else 0 end) as stock,
       sum(case when amount < 0 then amount else 0 end) as sold,
       sum(amount) over (order by week) as 
from t1
group by week;