Date ranges in T/SQL

Question

For a current project I am working I need to return an aggregate report based on date ranges.

I have 3 types of reports, yearly, monthly and daily.

To assis

Answer 1

From a performance standpoint, you will not want to use a function to generate the date ranges. For each evaluation in the query ( @myDate > dbo.MyFunc() ), the function will have to execute fully. Your best bet is to build static numbers table.

Now on with the numbers tables....

This is a fast way to create a integers table. (Props to Jeff Moden for the Identity Trick)

 SELECT TOP 1000000
        IDENTITY(INT,1,1) as N
   INTO dbo.NumbersTable
   FROM Master.dbo.SysColumns 
        Master.dbo.SysColumns 

Less than 2 seconds to populate 1000000 numbers in a table.

Now to address your problem, you will need to use this to build a table of dates. The example below will create a table with the zero hour (12AM) for each day starting from the @startDate

DECLARE @DaysFromStart int
DECLARE @StartDate datetime
SET @StartDate = '10/01/2008'

SET @ DaysFromStart  = (SELECT (DATEDIFF(dd,@StartDate,GETDATE()) + 1))

CREATE TABLE [dbo].[TableOfDates](
    [fld_date] [datetime] NOT NULL,
 CONSTRAINT [PK_TableOfDates] PRIMARY KEY CLUSTERED 
(
    [fld_date] ASC
)WITH FILLFACTOR = 99 ON [PRIMARY]
) ON [PRIMARY]


INSERT INTO
     dbo.TableOfDates
SELECT 
      DATEADD(dd,nums.n - @DaysFromStart ,CAST(FLOOR(CAST(GETDATE() as FLOAT)) as DateTime)) as FLD_Date
FROM #NumbersTable nums

SELECT MIN(FLD_Date) FROM dbo.TableOfDates
SELECT MAX(FLD_Date) FROM dbo.TableOfDates

Now with different combinations of DATEADD/DIFF, you should be able to create the static tables that you will need to do many date range queries efficiently.