根据数量列中的值将行拆分为多行

Question

我有一个包含产品信息和数量列的测试表。

 ProdID = 1 Qty = 3

在“数量”大于1的情况下，我需要为“数量”生成额外的行，因此输出将仅对每行具有Qty = 1：

 ProdID = 1 Qty = 1
 ProdID = 1 Qty = 1
 ProdID = 1 Qty = 1

我有点困惑，从哪里开始，我曾想过尝试添加一行然后每次减少数量，但这会循环，如何通过Set操作来完成...递归cte，交叉应用，可以它可以在tsql中完成吗？

with cte_test
as
(select a.* from 
(values('01-JAN-19','PROD1','BLUE',10.00, 1)
  ,('01-JAN-19','PROD1','RED',10.00, 1)
  ,('02-JAN-19','PROD1','BLUE',10.00, 2)
  ,('02-JAN-19','PROD2','BLUE',10.00, 1)
  ,('03-JAN-19','PROD1','RED',20.00, 6)
  ,('04-JAN-19','PROD1','BLUE',10.00, 1)
  ,('04-JAN-19','PROD3','BLACK',10.00, 3)
  ,('05-JAN-19','PROD1','BLUE',10.00, 2)
) as a ([Date],[Product],[Colour],[Price],[Qty])
)

select [Date],[Product],[Colour],[Price],[Qty] 
from cte_test

Answer 1

为此，我喜欢递归CTE：

with cte as (
      select [Date], [Product], [Colour], [Price], [Qty]
      from [TestTable]
      union all
      select [Date], [Product], [Colour], [Price], [Qty] - 1
      from cte
      where Qty > 1
     )
select [Date], [Product], [Colour], [Price], 1 as [Qty]
from cte;

如果Qty大于100，则需要添加option (maxrecursive 0) 。

Answer 2

使用递归CTE：

declare @maxqty int = (select max(qty) from [TestTable]);
with cte AS (
  select 1 qty
  union all
  select qty + 1 from cte where qty + 1 <= @maxqty
)
select [Date], [Product], [Colour], [Price], 1 as [Qty]
from [TestTable] t inner join cte c
on c.qty <= t.qty
order by [Date], [Product]

参见演示 。
结果：

> Date      | Product | Colour | Price | Qty
> :-------- | :------ | :----- | :---- | --:
> 01-JAN-19 | PROD1   | BLUE   | 10.00 |   1
> 01-JAN-19 | PROD1   | RED    | 10.00 |   1
> 02-JAN-19 | PROD1   | BLUE   | 10.00 |   1
> 02-JAN-19 | PROD1   | BLUE   | 10.00 |   1
> 02-JAN-19 | PROD2   | BLUE   | 10.00 |   1
> 03-JAN-19 | PROD1   | RED    | 10.00 |   1
> 03-JAN-19 | PROD1   | RED    | 10.00 |   1
> 03-JAN-19 | PROD1   | RED    | 10.00 |   1
> 03-JAN-19 | PROD1   | RED    | 10.00 |   1
> 03-JAN-19 | PROD1   | RED    | 10.00 |   1
> 03-JAN-19 | PROD1   | RED    | 10.00 |   1
> 04-JAN-19 | PROD1   | BLUE   | 10.00 |   1
> 04-JAN-19 | PROD3   | BLACK  | 10.00 |   1
> 04-JAN-19 | PROD3   | BLACK  | 10.00 |   1
> 04-JAN-19 | PROD3   | BLACK  | 10.00 |   1
> 05-JAN-19 | PROD1   | BLUE   | 10.00 |   1
> 05-JAN-19 | PROD1   | BLUE   | 10.00 |   1