Database

SELECT ...
       DATEDIFF(seconds,
                datecolumn1, 
                (SELECT TOP 1 datecolumn2 
                 FROM YourTable a1
                 WHERE ...
                 ORDER BY datecolumn2 DESC))
FROM YourTable
WHERE ...

...
WHERE a1.datecolumn1 < a.datecolumn1
...

....
Datediff(seconds, datecolumn, (Delete first row from datecolumn and add at the end null))

WITH Ordered AS (
    Select  IDColumn,DateColumn,ROW_NUMBER() OVER(ORDER BY DateColumn) as rn
    FROM    YourTable
    )
SELECT  o2.IDColumn,DateDiff(seconds,o2.DateColumn - o1.DateColumn)
FROM    ordered o1
join    ordered o2
on      o1.rn = o2.rn - 1

-- Copy Article stuff
DECLARE @List VARCHAR(1000), @Sql VarChar(5000)
SET @List = ''
SET @Sql = ''

IF EXISTS (SELECT * FROM tempdb.sys.objects
		WHERE name LIKE '#tblX%' AND type IN (N'U'))
	DROP TABLE [dbo].#tblX
	
CREATE TABLE #tblX(MixDate DateTime, NoMixes Int, MixPlant_Name VarChar(50) )
INSERT [#tblX]
SELECT DISTINCT(mp.MixDate), SUM(mp.NoMixes) As NoMixes, Mixplant.MixPlant_Name
	FROM MixProduction mp
	  INNER	JOIN MixPlant
	    ON mp.MixPlant_ID = Mixplant.ID And MixPlant.IsActive =1
	WHERE mp.MixDate BETWEEN '2/1/2011' AND '2/28/2011'
	Group By Mixplant.MixPlant_Name, mp.MixDate	
	
	
	
DECLARE @tblY TABLE(MixPlant_Name VarChar(50))
INSERT @tblY
  SELECT DISTINCT MixPlant_Name
    FROM #tblX
      ORDER BY MixPlant_Name
		
 SELECT @List = ISNULL(@List, '') +
		 CASE WHEN ISNULL(@List,'') = ''
		 THEN '[' + MixPlant_Name + ']'
		 ELSE ',[' + MixPlant_Name + ']' END
FROM @tblY
ORDER BY MixPlant_Name
		
SET @Sql = 'SELECT MixDate, ' + @List + CHAR(13)
SET @Sql = @Sql + 'FROM (SELECT MixDate, NoMixes, MixPlant_Name ' + CHAR(13)
SET @Sql = @Sql + 'FROM #tblX ) As P ' + CHAR(13)
SET @Sql = @Sql + 'PIVOT (SUM(NoMixes) FOR MixPlant_Name IN (' + @List + ')) As Pvt' + CHAR(13)
	
-- test output
--print @sql
--SELECT * FROM #tblX
	
-- exucute dynamic sql
Exec (@Sql)
	
-- Drop Table
DROP TABLE #tblX
GO