计算没有临时年表的活动项目/年份

Question

具有以下记录结构：

<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＆gt; = 2008和Firebird＆gt; = 2.5）每年有多少项有效？结果应该是：

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

我使用了包含系列（1900..2100）的temorary表，并使用BETWEEN和extract（year ..）连接原始表和临时表。但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

这就是我使用辅助函数的方法。

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]

这是辅助函数，我有很多它们，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