Generate a resultset of incrementing dates in TSQL

Question

Consider the need to create a resultset of dates. We've got start and end dates, and we'd like to generate a list of dates in between.

DECLARE  @Start datetime
         ,@End  datetime
DECLARE @AllDates table
        (@Date datetime)

SELECT @Start = 'Mar 1 2009', @End = 'Aug 1 2009'

--need to fill @AllDates. Trying to avoid looping. 
-- Surely if a better solution exists.

Consider the current implementation with a WHILE loop:

DECLARE @dCounter datetime
SELECT @dCounter = @Start
WHILE @dCounter <= @End
BEGIN
 INSERT INTO @AllDates VALUES (@dCounter)
 SELECT @dCounter=@dCounter+1 
END

Question: How would you create a set of dates that are within a user-defined range using T-SQL? Assume SQL 2005+. If your answer is using SQL 2008 features, please mark as such.

Solution 1

If your dates are no more than 2047 days apart:

declare @dt datetime, @dtEnd datetime
set @dt = getdate()
set @dtEnd = dateadd(day, 100, @dt)

select dateadd(day, number, @dt)
from 
    (select number from master.dbo.spt_values
     where [type] = 'P'
    ) n
where dateadd(day, number, @dt) < @dtEnd

I updated my answer after several requests to do so. Why?

The original answer contained the subquery

 select distinct number from master.dbo.spt_values
     where name is null

which delivers the same result, as I tested them on SQL Server 2008, 2012, and 2016.

However, as I tried to analyze the code that MSSQL internally when querying from spt_values, I found that the SELECT statements always contain the clause WHERE [type]='[magic code]'.

Therefore I decided that although the query returns the correct result, it delivers the correct result for wrong reasons:

There may be a future version of SQL Server which defines a different [type] value which also has NULL as values for [name], outside the range of 0-2047, or even non-contiguous, in which case the result would be simply wrong.

Solution 2

Tthe following uses a recursive CTE (SQL Server 2005+):

WITH dates AS (
     SELECT CAST('2009-01-01' AS DATETIME) 'date'
     UNION ALL
     SELECT DATEADD(dd, 1, t.date) 
       FROM dates t
      WHERE DATEADD(dd, 1, t.date) <= '2009-02-01')
SELECT ...
  FROM TABLE t
  JOIN dates d ON d.date = t.date --etc.

Solution 3

@KM's answer creates a numbers table first, and uses it to select a range of dates. To do the same without the temporary numbers table:

DECLARE  @Start datetime
         ,@End  datetime
DECLARE @AllDates table
        (Date datetime)

SELECT @Start = 'Mar 1 2009', @End = 'Aug 1 2009';

WITH Nbrs_3( n ) AS ( SELECT 1 UNION SELECT 0 ),
     Nbrs_2( n ) AS ( SELECT 1 FROM Nbrs_3 n1 CROSS JOIN Nbrs_3 n2 ),
     Nbrs_1( n ) AS ( SELECT 1 FROM Nbrs_2 n1 CROSS JOIN Nbrs_2 n2 ),
     Nbrs_0( n ) AS ( SELECT 1 FROM Nbrs_1 n1 CROSS JOIN Nbrs_1 n2 ),
     Nbrs  ( n ) AS ( SELECT 1 FROM Nbrs_0 n1 CROSS JOIN Nbrs_0 n2 )

    SELECT @Start+n-1 as Date
        FROM ( SELECT ROW_NUMBER() OVER (ORDER BY n)
            FROM Nbrs ) D ( n )
    WHERE n <= DATEDIFF(day,@Start,@End)+1 ;

Test of course, if you are doing this often, a permanent table may well be more performant.

The query above is a modified version from this article, which discusses generating sequences and gives many possible methods. I liked this one as it does not create a temp table, and is not limited to the number of elements in the sys.objects table.

Solution 4

This solution is based on marvelous answer of the same question for MySQL. It is also very performant on MSSQL. https://stackoverflow.com/a/2157776/466677

select DateGenerator.DateValue from (
  select DATEADD(day, - (a.a + (10 * b.a) + (100 * c.a) + (1000 * d.a)), CONVERT(DATE, GETDATE()) ) as DateValue
  from (select a.a from (values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) as a(a)) as a
  cross join (select b.a from (values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) as b(a)) as b
  cross join (select c.a from (values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) as c(a)) as c
  cross join (select d.a from (values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) as d(a)) as d
) DateGenerator
WHERE DateGenerator.DateValue BETWEEN 'Mar 1 2009' AND 'Aug 1 2009'
ORDER BY DateGenerator.DateValue ASC

works only for dates in the past, for dates in future change minus sign in DATEADD function. Query works only for SQL Server 2008+ but could be rewritten also for 2005 by replacing "select from values" construct with unions.

Solution 5

For this method to work, you need to do this one time table setup:

SELECT TOP 10000 IDENTITY(int,1,1) AS Number
    INTO Numbers
    FROM sys.objects s1
    CROSS JOIN sys.objects s2
ALTER TABLE Numbers ADD CONSTRAINT PK_Numbers PRIMARY KEY CLUSTERED (Number)

Once the Numbers table is set up, use this query:

SELECT
    @Start+Number-1
    FROM Numbers
    WHERE Number<=DATEDIFF(day,@Start,@End)+1

to capture them do:

DECLARE  @Start datetime
         ,@End  datetime
DECLARE @AllDates table
        (Date datetime)

SELECT @Start = 'Mar 1 2009', @End = 'Aug 1 2009'

INSERT INTO @AllDates
        (Date)
    SELECT
        @Start+Number-1
        FROM Numbers
        WHERE Number<=DATEDIFF(day,@Start,@End)+1

SELECT * FROM @AllDates

output:

Date
-----------------------
2009-03-01 00:00:00.000
2009-03-02 00:00:00.000
2009-03-03 00:00:00.000
2009-03-04 00:00:00.000
2009-03-05 00:00:00.000
2009-03-06 00:00:00.000
2009-03-07 00:00:00.000
2009-03-08 00:00:00.000
2009-03-09 00:00:00.000
2009-03-10 00:00:00.000
....
2009-07-25 00:00:00.000
2009-07-26 00:00:00.000
2009-07-27 00:00:00.000
2009-07-28 00:00:00.000
2009-07-29 00:00:00.000
2009-07-30 00:00:00.000
2009-07-31 00:00:00.000
2009-08-01 00:00:00.000

(154 row(s) affected)

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