如何在月和年列中返回60组月和年数据？

Question

我提供了两个整数类型的变量，@month 和 @year（因此月份是 1、2、3、... 9、10、11、12，而年份是四位数的年份）。

我要做的是创建一个表值函数，它将接受这两个参数并返回过去 60 个月，然后到 2005 年结束。

例如，对于@month = 1 和@year = 2018，我希望返回此表：

+----+------+
| 1  | 2018 |
+----+------+
| 12 | 2017 |
+----+------+
| 11 | 2017 |
+----+------+
| 10 | 2017 |
+----+------+
| 9  | 2017 |
+----+------+
| 8  | 2017 |
+----+------+
| 7  | 2017 |
+----+------+
| 6  | 2017 |
+----+------+
| 5  | 2017 |
+----+------+
| 4  | 2017 |
+----+------+
| 3  | 2017 |
+----+------+
| 2  | 2017 |
+----+------+
| 1  | 2017 |
+----+------+
| 12 | 2016 |
+----+------+
| 11 | 2016 |
+----+------+
| 10 | 2016 |
+----+------+
| 9  | 2016 |
+----+------+
| 8  | 2016 |
+----+------+
| 7  | 2016 |
+----+------+
| 6  | 2016 |
+----+------+
| 5  | 2016 |
+----+------+
| 4  | 2016 |
+----+------+
| 3  | 2016 |
+----+------+
| 2  | 2016 |
+----+------+
| 1  | 2016 |
+----+------+
| 12 | 2015 |
+----+------+
| 11 | 2015 |
+----+------+
| 10 | 2015 |
+----+------+
| 9  | 2015 |
+----+------+
| 8  | 2015 |
+----+------+
| 7  | 2015 |
+----+------+
| 6  | 2015 |
+----+------+
| 5  | 2015 |
+----+------+
| 4  | 2015 |
+----+------+
| 3  | 2015 |
+----+------+
| 2  | 2015 |
+----+------+
| 1  | 2015 |
+----+------+
| 12 | 2014 |
+----+------+
| 11 | 2014 |
+----+------+
| 10 | 2014 |
+----+------+
| 9  | 2014 |
+----+------+
| 8  | 2014 |
+----+------+
| 7  | 2014 |
+----+------+
| 6  | 2014 |
+----+------+
| 5  | 2014 |
+----+------+
| 4  | 2014 |
+----+------+
| 3  | 2014 |
+----+------+
| 2  | 2014 |
+----+------+
| 1  | 2014 |
+----+------+
| 12 | 2013 |
+----+------+
| 11 | 2013 |
+----+------+
| 10 | 2013 |
+----+------+
| 9  | 2013 |
+----+------+
| 8  | 2013 |
+----+------+
| 7  | 2013 |
+----+------+
| 6  | 2013 |
+----+------+
| 5  | 2013 |
+----+------+
| 4  | 2013 |
+----+------+
| 3  | 2013 |
+----+------+
| 2  | 2013 |
+----+------+
| 12 | 2012 |
+----+------+
| 12 | 2011 |
+----+------+
| 12 | 2010 |
+----+------+
| 12 | 2009 |
+----+------+
| 12 | 2008 |
+----+------+
| 12 | 2007 |
+----+------+
| 12 | 2006 |
+----+------+
| 12 | 2005 |
+----+------+

我正在考虑用几种方法来做这件事，也许是交叉连接，或者是一些 while 循环——但它们似乎真的效率低下。我认为这不是最难的，但我想为它写“好”的代码。一段时间以来，我一直在思考“最好”的方式。

不幸的是，我对数据如何到达我没有任何发言权，这是我需要给出的回报，否则我会使用日期数据类型和日期函数。

Answer 1

我的偏好是将其保存在表格中。基本上，根据需要创建一个表，然后让它进入大约 50 年的未来。然后，您的函数可以从该表中进行选择。

表：

create table MonthDim
(
PK_ID int identity(1, 1) primary key,
Month int,
Year int,
Dt date --set this to the first of each month
)

查询：

select *
from MonthDim
where dt >= dateadd(month, -60, datefromparts(@year, @month, 1))
    and dt <= datefromparts(@year, @month, 1)

union all

select *
from MonthDim
where dt < dateadd(month, -60, datefromparts(@year, @month, 1))
    and Month = 12

这样做的额外好处是，由于它是持久的，如果您需要保存下游生成的任何数据，您可以在此处引用主键。也更容易理解发生了什么。

Answer 2

这使用递归 CTE。如果您的环境允许，我自然会使用dimension table。这是一种方式，但最好的方式当然值得商榷。

declare @year int = 2018
declare @month int = 1



;with cte as(
    select [Month], [Year] = 2005
    from  (values(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12)) as X([Month]) 
    union all
    select [Month], [Year] + 1
    from cte
    where [Year] < @year
),

someYears as(
select [Years] = 2005
union all
select [Years] + 1
from someYears
where [Years] < @year),

t as(
select  *, RN = row_number() over (order by [Year] desc, [Month] desc) 
from cte
where [Month] <= case when [Year] = @year then @month else 13 end)


select [Month], [Year]
from t
where RN <= 60
union 
select 12, [Years]
from (select [Years] from someYears) x
where x.Years < @year
order by [Year] desc, [Month] desc