窗口功能 - 通过重置运行总计

Question

我正在使用SQL Server 2012来构建库存计划/重新排序引擎.

我有一堆过时的交易,称之为信用和借记.我想一次做两件事:

1. 生成运行总计(每日净余额)
2. 生成补充建议.补货会将Running Total(在#1中)重置为零.

该表如下所示:

CREATE TABLE TX (TDate DATETIME, Qty   INT);

INSERT INTO TX VALUES ('2014-03-01', 20);  
INSERT INTO TX VALUES ('2014-03-02',-10); 
INSERT INTO TX VALUES ('2014-03-03',-20); 
INSERT INTO TX VALUES ('2014-03-04',-10); 
INSERT INTO TX VALUES ('2014-03-05', 30); 
INSERT INTO TX VALUES ('2014-03-06',-20);  
INSERT INTO TX VALUES ('2014-03-07', 10);  
INSERT INTO TX VALUES ('2014-03-08',-20); 
INSERT INTO TX VALUES ('2014-03-09', -5);  

我正在使用SQL 2012 SUM OVER()窗口函数来显示这些的运行总计.

select TDate, Qty, RunningTotal, RecommendedReplenish from (
    select 
        TDate, 
        Qty, 
        SUM(Qty) OVER (ORDER BY TDate ROWS UNBOUNDED PRECEDING)  as RunningTotal,
        -1 * (CASE WHEN Qty < 0 AND SUM(Qty) OVER (ORDER BY TDate ROWS UNBOUNDED     PRECEDING) < 0 
                THEN 
            CASE WHEN Qty >  SUM(Qty) OVER (ORDER BY TDate ROWS UNBOUNDED PRECEDING)     THEN Qty ELSE SUM(Qty) OVER (ORDER                        BY TDate ROWS UNBOUNDED PRECEDING) END
        ELSE 0 END) as RecommendedReplenish
        /* Wrong, does not account for balance resetting to zero */
    from TX 
) T order by TDate

如果它低于零,我需要找到一种方法将运行总计(也就是RT)重置为零.

我的查询,其中数量和RT均为负数,并且将这些数据作为第一次推荐补充的更多(更少负面).这是第一次正常工作.

我不知道如何从窗口运行总计中扣除这个..如果可能的话,我想在单个语句中执行此操作.

以下是我要求的输出摘要:

TDate        Qty    R.Tot  Replenish     New RT
-----------  ----   -----  -----------  ---------
3/1/2014     20      20                    20
3/2/2014    -10      10                    10
3/3/2014    -20     -10       10            0
3/4/2014    -10     -20       10            0
3/5/2014     30      10                    30
3/6/2014    -20     -10                    10
3/7/2014     10       0                    20
3/8/2014    -20     -20                     0
3/9/2014    - 5     -25        5            0

Itzik Ben-Gan,Joe Celko或其他SQL英雄,你在外面吗？:)

提前致谢!

Answer 1

这可以使用基于集合的解决方案来完成:

1.计算正常运行总量(称之为RT)

2.计算RT的运行最小值(称之为MN)

当MN为负数时,-MN是到目前为止您必须补充的总量.当MN为负时,令replenish_rt为-MN.因此,新的运行总计(称为new_rt)是rt + replenish_rt.如果您需要返回所需的当前补货数量,请从当前减去过去的replenish_rt(使用LAG).

这是完整的解决方案查询:

with c1 as
(
  select *,
    sum(qty) over(order by tdate rows unbounded preceding) as rt
  from tx
),
c2 as
(
  select *,
    -- when negative, mn is the total qty that had to be
    -- replenished until now, inclusive
    min(rt) over(order by tdate rows unbounded preceding) as mn_cur
  from c1
)
select tdate, qty, rt,
  replenish_rt - lag(replenish_rt, 1, 0) over(order by tdate) as replenish,
  rt + replenish_rt as new_rt
from c2
  cross apply(values(case when mn_cur < 0 then -mn_cur else 0 end)) as a1(replenish_rt);

干杯,Itzik