Question

I have a table that looks like this:

DECLARE @myTable TABLE (SampleID varchar(max), site varchar(max), SPDate date)  
  INSERT @myTable
    SELECT 'A-1', 1, '9/1/2012'   UNION ALL
    SELECT 'A-2', 1, '10/1/2012'  UNION ALL
    SELECT 'A-3', 1, '10/15/2012' UNION ALL
    SELECT 'A-5', 1, '5/1/2012'   UNION ALL
    SELECT 'A-4', 1, '1/1/2012'   UNION ALL
    SELECT 'B-1', 2, '11/1/2012'  UNION ALL
    SELECT 'B-2', 2, '8/1/2012'   UNION ALL
    SELECT 'B-3', 2, '5/1/2012'   UNION ALL
    SELECT 'B-4', 2, '4/1/2012'   UNION ALL
    SELECT 'C-1', 3, '10/1/2012'  UNION ALL
    SELECT 'C-2', 3, '10/15/2012' UNION ALL
    SELECT 'C-3', 3, '7/1/2012' ; 

What I would like to have is a query that gives me all the dates that are > 75 days from today and then sorted in descending order (e.g. the most recent date first).

So for my table, the output would look like this:

    Site1    Site2   Site3
     A-1      B-2     C-2
     A-5      B-3     C-3
     A-4      B-4

So I know how I can make the Site1, Site2 and Site3 queries separate like this

 SELECT SampleID FROM @myTable
     WHERE  DATEDIFF(DAY, SPDate, GETDATE()) > 75 AND
     site=1 ORDER BY SPDate DESC

How do I make these three queries into one table ?

Thanks !

Answer 1

You can easily perform this using the PIVOT function. If you have only the 3 site values that you show above, then you can hard-code the values, similar to this:

select [Site1], [Site2], [Site3]
from
(
  select SampleID, 
    'Site'+ cast(site as varchar(10)) SiteNumber
     ,row_number() over(partition by site order by spdate desc) rn
  from myTable 
  where DateDiff(day, spdate, getdate()) >75
) src
pivot
(
  max(SampleID)
  for SiteNumber in ([Site1], [Site2], [Site3])
) piv;

See SQL Fiddle with Demo

But is you have an unknown number of sites, then you can implement a dynamic sql version of this:

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT distinct ',' + QUOTENAME('Site'+ site) 
                    from myTable
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT ' + @cols + ' from 
             (
               select SampleID, 
                 ''Site''+ cast(site as varchar(10)) SiteNumber
                  ,row_number() over(partition by site order by spdate desc) rn
               from myTable 
               where DateDiff(day, spdate, getdate()) >75
            ) x
            pivot 
            (
                max(SampleID)
                for SiteNumber in (' + @cols + ')
            ) p '

execute(@query)

See SQL Fiddle with Demo

Both generate the same result:

| SITE1 | SITE2 |  SITE3 |
--------------------------
|   A-1 |   B-2 |    C-3 |
|   A-5 |   B-3 | (null) |
|   A-4 |   B-4 | (null) |