Question

Given a table of projects with start and end dates as well as a region that they are taking place, I am trying to get my result to output the number of active projects per week over a given interval and grouped by region.

I have many records in Projects that look like

region         start_date         end_date
Alabama        2012-07-08         2012-08-15
Texas          2012-06-13         2012-07-24
Alabama        2012-07-25         2012-09-13
Texas          2012-08-08         2012-10-28
Florida        2012-07-03         2012-08-07
Lousiana       2012-07-14         2012-08-12
....

If I want results for a single week, I can do something like

DECLARE @today datetime
SET @today ='2012-11-09'

SELECT 
[Region],
count(*) as ActiveProjectCount
FROM [MyDatabase].[dbo].[Projects]
where (datecompleted is null and datestart < @today) OR (datestart < @today AND @today     < datecompleted)
Group by region
order by region asc

This produces

Region           ActiveProjectCount
Arkansas                15
Louisiana               18
North Dakota            18
Oklahoma                27
...

How can I alter this query to produce results that look like

Region          10/06   10/13   10/20   10/27    
Arkansas          15      17      12      14
Louisiana          3       0       1       5
North Dakota      18      17      16      15
Oklahoma          27      23      19      22
...

Where on a weekly interval, I am able to see the total number of active projects (projects between start and end date)

Answer 1

you could do sth. like this:

with "nums"
as
(
  select 1 as "value"
  union all select "value" + 1 as "value"
  from "nums"
  where "value" <= 52
)
, "intervals"
as
(
  select
  "id" = "value"
  , "startDate" = cast( dateadd( week, "value" - 1, dateadd(year, datediff(year, 0, getdate()), 0)) as date )
  , "endDate" = cast( dateadd( week, "value", dateadd( year, datediff( year, 0, getdate()), 0 )) as date )

from
  "nums"
)
, "counted"
as
(
select
  "intervalId" = I."id"
  , I."startDate"
  , I."endDate"
  , D."region"
  , "activeProjects" = count(D."region") over ( partition by I."id", D."region" )

from
  "intervals" I
  inner join "data" D
    on D."startDate" <= I."startDate"
    and D."endDate" > I."endDate"
)

select
  *
from
(
  select
    "region"
    , "intervalId"
  from
    "counted"
) as Data
pivot
( count(Data."intervalId") for intervalId in ("25", "26", "27", "28", "29", "30", "31")) as p

intervals can be defined as you wish.

see SQL-Fiddle