Question

I have this RoomTable with value

SID   Room   Date        APhase   BPhase   ACount  BCount
1     One    10/28/2012  4        5         3       6
2     One    10/29/2012  2        3        -1      -1
3     One    10/30/2012  4        5         7      -1
4     Two    10/28/2012  8        3         2       3
5     Two    10/30/2012  3        5         4       6
6     Three  10/29/2012  5        8         2      -1
7     Three  10/30/2012  5        6        -1       4
8     Four   10/29/2012  6        2        -1      -1
9     Four   10/30/2012  5        8        -1      -1

What I want is to return the following:

1. Total sum of APhase and BPhase of each Room.
2. Value of ACount and BCount from max date of each Room
3. If ACount value is -1 then use the previous date. Same as BCount.
4. If ACount value is -1 and the previous date is -1 and so on. Then use 0. Same as BCount.

I can get the query of number 1 with this query

SELECT Room, sum(APhase) as TotalAPhase, sum(BPhase) as TotalBPhase 
FROM RoomTable 
WHERE Date between '10/28/2012' and '10/30/2012'
group by Room
order by Room

But I’m confused on how to include the number 2-4 query.

This is the output I want

Room  TotalAPhase  TotalBPhase  ACount   BCount
One   10           13           7        6
Two   11           8            4        6
Three 10           13           2        4
Four  11           10           0        0

Any ideas will be much appreciated. Thanks.

Answer 1

Hope this works for your case:

SELECT 
Room
,SUM(APhase) AS TotalAPhase
,SUM(BPhase) AS TotalBPhase 
,ISNULL((    SELECT TOP 1 RT1.ACount 
             FROM RoomTable RT1 
             WHERE RT1.Room = RT.Room 
                AND RT1.ACount != -1
             ORDER BY RT1.Date DESC
), 0) AS ACount
,ISNULL((   SELECT TOP 1 RT2.BCount 
            FROM RoomTable RT2
            WHERE RT2.Room = RT.Room 
               AND RT2.BCount != -1
            ORDER BY RT2.Date DESC
), 0) AS BCount

FROM RoomTable RT
--WHERE Date between '10/28/2012' and '10/30/2012'
GROUP BY Room
ORDER BY Room

I am not sure if you really need that where clause so I commented it out. And the value of TotalBPhase for Room Three on your result table should be 14, as can be seen from this SQL Fiddle demo.