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SQL:   Data Sets - Reserved vs Available Dates

Posted on 2007-11-29
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Last Modified: 2010-04-21
I have a table with reservation dates.  I would like to create a query that returns the dates not in the reservation table...for a given date range.  Is there a simple way to do this without.

I basicly need to return a set of 'interesting' dates....and the interest is availability.
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Question by:Paulconsulting
4 Comments
 
LVL 22

Expert Comment

by:dportas
ID: 20376880
SELECT dt
FROM Calendar
WHERE dt >= '20070101'
 AND dt < '20080101'
EXCEPT
SELECT dt
FROM Reservations;
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LVL 70

Expert Comment

by:Scott Pletcher
ID: 20377268
SELECT c.date
FROM calendar c
LEFT OUTER JOIN reservations r ON c.date = r.date
WHERE r.date IS NULL
AND c.date BETWEEN 'startDate' AND 'endDate'
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LVL 32

Accepted Solution

by:
Brendt Hess earned 500 total points
ID: 20377363
The simplest way is to use a calendar table or, more versatilely, a numbers table with DATEDIFF.  This example uses a numbers table with numbers from 0 to 8192 (which should be a long enough range).

CREATE TABLE Numbers (value int primary key)

INSERT INTO Numbers Values (0)
Insert Into Numbers Values (1)

INSERT INTO Numbers SELECT Value + 2 FROM Numbers
INSERT INTO Numbers SELECT Value + 4 FROM Numbers
INSERT INTO Numbers SELECT Value + 8 FROM Numbers
INSERT INTO Numbers SELECT Value + 16 FROM Numbers
INSERT INTO Numbers SELECT Value + 32 FROM Numbers
INSERT INTO Numbers SELECT Value + 64 FROM Numbers
INSERT INTO Numbers SELECT Value + 128 FROM Numbers
INSERT INTO Numbers SELECT Value + 256 FROM Numbers
INSERT INTO Numbers SELECT Value + 512 FROM Numbers
INSERT INTO Numbers SELECT Value + 1024 FROM Numbers
INSERT INTO Numbers SELECT Value + 2048 FROM Numbers
INSERT INTO Numbers SELECT Value + 4096 FROM Numbers


Now that we have our table, let's see what we can do with it:

Assume that our interested date range is from Jan 15, 2007 to June 15, 2007

SELECT Dateadd(Day, N.Value, '20070115')
FROM Numbers N
LEFT JOIN ReservationDates rd
    ON Dateadd(Day, N.Value, '20070115') = rd.ReservedDate
WHERE N <= Datediff(Day, '20070115', '20070615')
    AND rd.ReservedDate is null

Clearly, a table with all dates would also work.  But the numbers table allows for more versatility with a smaller table (need to query a range back in 1980?  No need to have all of the dates in the table).
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Author Closing Comment

by:Paulconsulting
ID: 31411776
Works great!
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