SQL查询按条件按周计数

Question

我必须按星期编写数据库中脚手架数量的趋势报告。 在下面的示例中，我可以获得按周竖起的脚手架数量，也可以使用相同的查询将其拆除，但这不是我所需要的。

SELECT COUNT(scaffID) Erected, WeekStart
FROM 
(
 SELECT ScaffID, 
        dateadd(week, datediff(day,0,Erected) / 7, 0) AS WeekStart  
 FROM Scaffolds
) o
GROUP BY WeekStart

我可以通过指定日期从中获得站立式脚手架，但我希望每个星期五都说站立式脚手架。

Declare @staticDate As DateTime
Set @staticDate = '2/1/2015'

Select COUNT(scaffID) As StandingScaffolds
from RequestInfo 
Where (    ErectDate<= @staticDate )
  And (    DismantleDate>= @staticDate
        or DismantleDate Is NULL
      )

这让我发疯，所以我们将不胜感激。

菲尔

Answer 1

这应该给您一些开始。

DECLARE     
    @startDate date = '2015-01-01',
    @endDate date = '2015-01-28';

with myWeeks (myWeek) AS (
    select DATEPART(WEEK,@startDate) myWeek
    UNION ALL
    select myWeek + 1 from myWeeks
    where
        myWeek < DATEPART(WEEK,@endDate)
)
select 
    w,
    COUNT(s.Erected) standingScaffolds
from myWeeks w
left join Scaffolds s on
    w.myWeek between DATEPART(WEEK,s.Erected) and DATEPART(WEEK,s.Dismantled)

Answer 2

您可能要为此生成一个日期表（=每天有一行的表）。 然后，您可以将其与该表连接起来以很容易地获得计算结果。

select d.date, count(s.scaffID)
from date d, scaffolds s
where s.erected <= d.date and
(dismantled>= d.date or dismantled is NULL) and
d.date >= @stardate and
d.date <= enddate
group by d.date

希望这没关系，现在无法测试。

日期表在其他情况下也非常有用，例如，您可以在那里度过当地假期。