计数有效的项目/年无临时今年表

Question

用下面的记录结构：

<item> | <start> | <stop> 
Item-A | 2013-04-05 | 2014-06-07 
Item-B | 2012-06-07 | 2015-03-07 

是否可以使用SQL查询（在MS-SQL> = 2008和火鸟> = 2.5）多少个项目每年都活跃？结果应该是：

2012 | 1 
2013 | 2 
2014 | 2 
2015 | 1 

我用含系列（1900..2100）一temorary表和使用之间的连接源表和临时表，并提取（年..）。但是我正在寻找更好的解决方案，而不使用额外的表格。

Answer 1

这符合您的要求。

select Years.[Year], 
     count(1) [Count] 
from MyTable mt 
join (select distinct(year(start)) as [Year] 
     from MyTable 

     union 

     select distinct(year(stop)) 
     from MyTable 

     union 

     select year(getdate()) 
     from MyTable 
     where exists 
      (select 1 
      from MyTable 
      where stop is null)) as Years 
on Years.[Year] between Year(mt.start) and Year(isnull(mt.stop, getdate())) 
group by Years.[Year] 
order by Years.[Year] 

Answer 2

这就是我将如何使用帮助函数。

declare @StartMin datetime 
declare @StopMax datetime 

select @StartMin = min(start), 
@StopMax = max(isnull(stop, getdate())) 
from MyTable 

select Years.[Year], 
count(1) [Count] 
from MyTable mt 
join [dbo].[YearsBetween](@StartMin, @StopMax) as Years 
on Years.[Year] between Year(mt.start) and Year(isnull(mt.stop, getdate())) 
group by Years.[Year] 
order by Years.[Year] 

这是辅助功能，我有很多人，DatesBetween，MonthsBetween，NumbersBetween等

create function [dbo].[YearsBetween](@Start datetime, @Stop datetime) 
returns @Years TABLE 
(
[Year] int 
) 
begin 
declare @StartYear int 
declare @StopYear int 

set @StartYear = year(@Start) 
set @StopYear = year(@Stop) 

while(@StartYear <= @StopYear) 
begin 
    insert into @Years 
    values(@StartYear) 

    set @StartYear = @StartYear + 1 
end 

return; 
end