SQL Server 2008 - Enumerate multiple date ranges - sql

Question

How can I enumerate multiple date ranges in SQL Server 2008? I know how to do this if my table contains a single record
StartDate EndDate
2014-01-01 2014-01-03
;WITH DateRange
AS (
SELECT #StartDate AS [Date]
UNION ALL
SELECT DATEADD(d, 1, [Date])
FROM DateRange
WHERE [Date] < #EndDate
)
SELECT * FROM DateRange
OUTPUT
2014-01-01, 2014-01-02, 2014-01-03
I am however lost as how to do it if my table contains multiple records. I could possibly use the above logic in a cursor but want to know if there is a set based solution instead.
StartDate EndDate
2014-01-01 2014-01-03
2014-01-05 2014-01-06
DESIRED OUTPUT:
2014-01-01, 2014-01-02, 2014-01-03, 2014-01-05, 2014-01-06

Answer 1

Well, let's see. Define the ranges as a table. Then generate the full range of dates from the first to the last date. Finally, select the dates that are in the range:
with dateranges as (
select cast('2014-01-01' as date) as StartDate, cast('2014-01-03' as date) as EndDate union all
select '2014-01-05', '2014-01-06'
),
_dates as (
SELECT min(StartDate) AS [Date], max(EndDate) as enddate
FROM dateranges
UNION ALL
SELECT DATEADD(d, 1, [Date]), enddate
FROM _dates
WHERE [Date] < enddate
),
dates as (
select [date]
from _dates d
where exists (select 1 from dateranges dr where d.[date] >= dr.startdate and d.[date] <= dr.enddate)
)
select *
from dates
. . .
You can see this work here.

Answer 2

You could grab the min and max dates first, like so:
SELECT #startDate = MIN(StartDate), #endDate = MAX(EndDate)
FROM YourTable
WHERE ...
And then pass those variables into your date range enumerator.
Edit... Whoops, I missed an important requirement. See the accepted answer.

Answer 3

As GordonLinoff mentioned, you should:
Store your ranges in a table
Generate a range of dates that encompasses your ranges
Filter down to only those dates that fall within the range
The following query builds up a collection of numbers, and then uses that to quickly generate all of the dates that fall within each range.
-- Create a table of digits (0-9)
DECLARE #Digits TABLE (digit INT NOT NULL PRIMARY KEY);
INSERT INTO #Digits(digit)
VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
WITH
-- Store our ranges in a common table expression
CTE_DateRanges(StartDate, EndDate) AS (
SELECT '2014-01-01', '2014-01-03'
UNION ALL
SELECT '2014-01-05', '2014-01-06'
)
SELECT DATEADD(DAY, NUMBERS.num, RANGES.StartDate) AS Date
FROM
(
-- Create the list of all 3-digit numbers (0-999)
SELECT D3.digit * 100 + D2.digit * 10 + D1.digit AS num
FROM #Digits AS D1
CROSS JOIN #Digits AS D2
CROSS JOIN #Digits AS D3
-- Add more CROSS JOINs to #Digits if your ranges span more than 999 days
) NUMBERS
-- Join to our ranges table to generate the dates and filter them
-- down to those that fall within a range
INNER JOIN CTE_DateRanges RANGES
ON DATEADD(DAY, NUMBERS.num, RANGES.StartDate) <= RANGES.EndDate
ORDER BY
Date
The date creation is done by joining our number list with our date ranges, using the number as a number of days to add to the StartDate of the range. We then filter out any results where the generated date for a given range falls beyond that range's EndDate. Since we're adding a non-negative number of days to the StartDate to generate the date, we know that our date will always be greater-than-or-equal-to the StartDate of the range, so we don't need to include StartDate in the WHERE clause.
This query will return DATETIME values. If you need a DATE value, rather than a DATETIME value, you can simply cast the value in the SELECT clause.
Credit goes to Itzik Ben-Gan for the digits table.