T-SQL 在没有游标的行之间分配一个值

Question

我在 SQL Server 2014 上有一个简单的实际案例场景。我有一个 table 订单及其数量：

declare @qty_to_distribute int = 50

create table orders (id int, priority int, qty int)

insert into orders (id, priority, qty) values
(1, 1, 10),
(2, 2, 30),
(3, 3, 20),
(4, 4, 5)

我有一个值，例如 50，我必须根据它们的优先级在订单之间分配遍历订单

如果剩余数量大于当前订单数量，则该订单将被兑现，@qty_to_distribute减去订单数量，
如果不是 - 订单被取消。

查看示例数据 - 订单 1、2 和 4 将被实现，#3 被取消。

有没有简单的，有效的非光标解决方案，最好基于 window 函数？

这看起来很有希望，但不知道把条件放在哪里：

select id,
sum(qty) OVER (ORDER BY priority asc ROWS UNBOUNDED PRECEDING) as qtysum
from orders

id  qtysum
1   10
2   40
3   60      *
4   65      *

http://sqlfiddle.com/#!6/05fa2/2/0

Answer 1

已更新 感谢 Giorgi Nakeuri

WITH Intermediate AS (
  SELECT 
      Id, 
      ROW_NUMBER() OVER (ORDER BY Priority) as Priority, 
      qty                
  FROM Orders),
Result AS
(
    SELECT 
        Id, 
        Priority,
        CASE when qty < 50 THEN 0 ELSE qty END as Residual,
        CASE when qty < 50 THEN 50 - qty ELSE 50 END as Remaining   
    FROM Intermediate
    WHERE Priority = 1
    UNION ALL  
    SELECT  
         ORD.Id, 
         ORD.Priority, 
         CASE when ORD.qty < Result.Remaining THEN 0 ELSE qty END as Residual,
         CASE when ORD.qty < Result.Remaining THEN Result.Remaining - ORD.qty ELSE Result.Remaining END as Remaining
    FROM Intermediate ORD INNER JOIN Result ON ORD.Priority = Result.Priority + 1
  )
  select Id, Priority, Residual, Remaining from result

http://sqlfiddle.com/#!6/2ac98f/2

Answer 2

试试这个：

create table o (id int, priority int, qty int)

insert into o (id, priority, qty) values
(1, 1, 10),
(2, 2, 30),
(3, 3, 20),
(4, 4, 5),
(5, 5, 1),
(6, 6, 10)

with cte1 as(select *, row_number() over(order by priority) as rn from o),
cte2 as(
  select top 1 id, priority, qty, rn,
  case when qty > 50 then 1 else 0 end as ToBeCanceled
  from cte1 order by rn
    Union all
  select cte1.id, cte1.priority, case when cte2.qty + cte1.qty > 50 then cte2.qty
  else cte2.qty + cte1.qty end as qty,
  cte1.rn,
  case when cte2.qty + cte1.qty > 50 then 1 else 0 end as ToBeCanceled 
  from cte1
  join cte2 on cte1.rn = cte2.rn + 1)
select id, priority, ToBeCanceled from cte2
option(maxrecursion 0)

输出：

id  ToBeCanceled
1   0
2   0
3   1
4   0
5   0
6   1

Fiddle http://sqlfiddle.com/#!6/87ac9/19

T-SQL 在没有游标的行之间分配一个值

T-SQL distribute a value between rows without a cursor

tsql

sql-server

window-functions

sql-server-2014