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Query that Groups On Column but Excludes Certain Rows

Posted on 2008-06-20
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Last Modified: 2010-03-19
I have a RoomAvailability table for a Hotel booking engine.  Here's some sample data.  

1     6/24/2008 12:00:00 AM    0
1     6/25/2008 12:00:00 AM    1
1     6/26/2008 12:00:00 AM    0
1     6/27/2008 12:00:00 AM    0

Column 1 is the RoomNumber, Column 2 is a date, column 3 is a ReservationID.

Therefore, if someone needed to check in on 6/24 and check out  6/27 this particular room should not show up as a potential match because it is booked on 6/25.  So basically, I need a query that returns room numbers where that room has no reservationID on any day from the check-in to check-out dates.

I'm having a heck of a time thinking of a simple solution for this.  I can think of less elegant ways to bring back the correct data but I have a feeling that there is some T-Sql function or some recursive joining or something that will get me where i want to get.

I've attached my code so far.  Of course it doesn't work.   Anyone got any good ideas?
Select  RoomNumber
from    RoomAvailability
where   datediff(day,'06/24/2008',Date) >= 0 and 
        datediff(day,Date,'06/27/2008') >= 0
and ReservationID = 0
group by RoomNumber

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Question by:davidcahan
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Expert Comment

by:rickchild
ID: 21834401
Something like this, where the room must be available for at least the correct number of days in the range?

SELECT RoomNumber FROM RoomAvailability
WHERE
Room IN
(
    SELECT RoomNumber
    FROM RoomAvailability 
    WHERE ReservationID = 0 AND Date <= '2008-06-27' AND Date >= '2008-06-24' 
    GROUP BY RoomNumber
    HAVING count(RoomNumber) >=  ( DATEDIFF("dd",'2008-06-24','2008-06-27') +1 )
)

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Expert Comment

by:rickchild
ID: 21834422
Yeah should do it, just run that on some test data.  Just replace the dates with the correct variables.
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Accepted Solution

by:
rickchild earned 500 total points
ID: 21834748
Well, you don't really need the outside query ;-)
SELECT RoomNumber
    FROM RoomAvailability 
    WHERE ReservationID = 0 AND Date <= '2008-06-27' AND Date >= '2008-06-24' 
    GROUP BY RoomNumber
    HAVING count(RoomNumber) >=  ( DATEDIFF("dd",'2008-06-24','2008-06-27') +1 )

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Author Comment

by:davidcahan
ID: 21835161
actually...those don't work.  but i figured out that all i had to do was "reverse" my thinking.  if i find all the rooms that have a reservation between those dates then i can exclude them either using a "not in" statement or left joining back on RoomNumber:




Select RoomNumber
from RoomAvailability
where datediff(day,'06/24/2008',Date) >= 0 and 
		           datediff(day,Date,'06/27/2008') >= 0
and ReservationID = 1
group by RoomNumber

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Expert Comment

by:rickchild
ID: 21837027
Strange, I tested with the following which worked fine, maybe just seomthing to do with how I am setting the date in yyyy-mm-dd.  You are on SQL2005?
create table ##RoomAvailability (RoomNumber INT, Date datetime, ReservationID INT)
 
INSERT INTO ##RoomAvailability VALUES (1, '2008-06-24', 0)
INSERT INTO ##RoomAvailability VALUES (1, '2008-06-25', 1)
INSERT INTO ##RoomAvailability VALUES (1, '2008-06-26', 0)
INSERT INTO ##RoomAvailability VALUES (1, '2008-06-27', 0)
 
INSERT INTO ##RoomAvailability VALUES (2, '2008-06-24', 0)
INSERT INTO ##RoomAvailability VALUES (2, '2008-06-25', 0)
INSERT INTO ##RoomAvailability VALUES (2, '2008-06-26', 0)
INSERT INTO ##RoomAvailability VALUES (2, '2008-06-27', 0)
 
INSERT INTO ##RoomAvailability VALUES (3, '2008-06-24', 0)
INSERT INTO ##RoomAvailability VALUES (3, '2008-06-25', 1)
INSERT INTO ##RoomAvailability VALUES (3, '2008-06-26', 0)
INSERT INTO ##RoomAvailability VALUES (3, '2008-06-27', 0)
INSERT INTO ##RoomAvailability VALUES (3, '2008-06-28', 0)
 
INSERT INTO ##RoomAvailability VALUES (4, '2008-06-24', 0)
INSERT INTO ##RoomAvailability VALUES (4, '2008-06-25', 0)
INSERT INTO ##RoomAvailability VALUES (4, '2008-06-26', 0)
INSERT INTO ##RoomAvailability VALUES (4, '2008-06-27', 0)
INSERT INTO ##RoomAvailability VALUES (4, '2008-06-28', 0)
 
--- RETURNS ROOMS 2 & 4
SELECT RoomNumber
    FROM ##RoomAvailability 
    WHERE ReservationID = 0 AND Date <= '2008-06-27' AND Date >= '2008-06-24' 
    GROUP BY RoomNumber
    HAVING count(RoomNumber) >=  ( DATEDIFF("dd",'2008-06-24','2008-06-27') +1 )
 
 
--- RETURNS ROOM 4 ONLY
SELECT RoomNumber
    FROM ##RoomAvailability 
    WHERE ReservationID = 0 AND Date <= '2008-06-28' AND Date >= '2008-06-24' 
    GROUP BY RoomNumber
    HAVING count(RoomNumber) >=  ( DATEDIFF("dd",'2008-06-24','2008-06-28') +1 )

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Expert Comment

by:rickchild
ID: 21837051
Good idea with the NOT IN anyway, should also do it.

Upset that my solution didn't work for you as I did test it as above!
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Author Comment

by:davidcahan
ID: 21837449
let me try it again.  
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Author Comment

by:davidcahan
ID: 21842251
that is really weird, but it doesn't work.  i have no clue why.  i'm gonna give you points cause you did come up with a solution.

David
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Expert Comment

by:rickchild
ID: 21842281
OK thanks, must be some environment setting as it's a simple bit of testing!
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