5

I need to create a function that returns a table of continuous dates. I would pass in a min & max date.

I expect it to be able to be called like this:

SELECT * FROM GetDates('01/01/2009', '12/31/2009')

I currently have a stored proc that does this, but requirements changed and now I need to do include the returned data from within a union:

 with mycte as
(
     select cast(@minDate as datetime) DateValue
     union all
     select DateValue + 1
     from    mycte   
     where   DateValue + 1 <= @maxDate
 )
 select DateValue
 from    mycte
option (maxrecursion 1000)

The problem, however, is that I need to set the recursion to be greater than 100. According to a post by Gail Erickson [MS] on eggheadcafe, this is not currently supported.

Without creating a real (not temporary) table with just date in it, is there a way to do this?

I am using SqlServer2005.

OMG Ponies
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Nathan Koop
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  • It is possible to have recursion level set to a higher value than 100. If I remember correct the maximum supported level is 2^15. – Faiz Sep 08 '09 at 18:02

3 Answers3

6

Your best option is to actually have a physical table of dates. There aren't that many for even long periods, and will be much faster than materializing them on-the-fly from temp tables or recursive ctes.

Remus Rusanu
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    An intermediate solution, if you don't wish to have a table of dates is to use a [smaller] table of numbers (say from 0 to 1000) and to have something like select cast(@minDate as datetime) + Val from tblNumbers where val <= (cast(@minDate as datetime) - cast(@maxDate as datetime)) (assuming Val is the INT field in tblNumber, with values 0, 1, 2...) – mjv Sep 08 '09 at 18:15
  • Thanks, I've decided to go with the physical table, it just seems like a bad idea to have a table with one column storing just dates. – Nathan Koop Sep 08 '09 at 18:26
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    Is not a bad idea. It goes against the normal algorithm oriented way of thinking programers have, that's all. Actually many recommend having a table with just numbers, from 0 to 1 mil. or similar, to use in joins and queries similar to yours. – Remus Rusanu Sep 08 '09 at 18:37
3

If you choose to (or need to) go with an ad-hoc table and not a permanent one, this would do it:

CREATE FUNCTION dbo.DateList
 (
   @MinDate datetime
  ,@MaxDate datetime
 )
RETURNS TABLE
RETURN WITH
  Pass0 as (select 1 as C union all select 1), --2 rows
  Pass1 as (select 1 as C from Pass0 as A, Pass0 as B),--4 rows
  Pass2 as (select 1 as C from Pass1 as A, Pass1 as B),--16 rows
  Pass3 as (select 1 as C from Pass2 as A, Pass2 as B),--256 rows
  Pass4 as (select 1 as C from Pass3 as A, Pass3 as B),--65536 rows
  Tally as (select row_number() over(order by C) as Number from Pass4)
 select dateadd(dd, Number - 1, @MinDate) DateValue
 from Tally
 where Number < datediff(dd, @MindAte, @MaxDate) + 2

GO

And a testing call:

DECLARE
  @MinDate datetime
 ,@MaxDate datetime

SET @MinDate = 'Jan 1, 2009'
SET @MaxDate = 'Dec 31, 2009'

SELECT *
 from dbo.DateList(@MinDate, @MaxDate)

Wierd--this is the third SO post today that involved Tally tables. Must be some odd sunspot activity going on. Here are the linkes:

count number of rows that occur for each date in column date range.
What is the best way to create and populate a numbers table?

Community
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Philip Kelley
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1

something like this:

CREATE FUNCTION GetDates(@StartDate DateTime, @EndDate DateTime) 

RETURNS @Dates Table ( aDate DateTime Primary Key Not Null)
AS
BEGIN
 Declare @ThisDate DateTime Set @ThisDate = @StartDate  
 While @ThisDate < @EndDate begin      
      Insert @Dates (aDate) Values(@THisDate)      
      Set @ThisDate = @ThisDate + 1  
 End
RETURN 
END
GO

make sure @EndDate is after @startdate... Add input parameter checking to makes sure, or it could run forever if you pass it dates backwards

Charles Bretana
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