使用多个表并使用多个SUM函数的SQL

Question

I have looked over several posts that are relative but I cannot figure out how to apply them to my situation.

SELECT [LeisureActivities].[dbo].[activities].[activityID],
       [LeisureActivities].[dbo].[activities].[activityName],
       [LeisureActivities].[dbo].[activities].[activityDate],
       [LeisureActivities].[dbo].[activities].[activityPlaces],
       [LeisureActivities].[dbo].[activities].[activityPrice],
       SUM([LeisureActivities].[dbo].[bookings].[bookingPlaces]) AS 'bookingTotal',
       SUM([LeisureActivities].[dbo].[tempbookings].[tempPlaces]) AS 'tempPlacesReserved'

FROM   [LeisureActivities].[dbo].[activities],
       [LeisureActivities].[dbo].[bookings],
       [LeisureActivities].[dbo].[tempbookings]

WHERE ([LeisureActivities].[dbo].[activities].[activityID]=[LeisureActivities].[dbo].[bookings].[activityID] 
    AND [LeisureActivities].[dbo].[activities].[activityID]=[LeisureActivities].[dbo].[tempbookings].[tempActivityID]) 
    AND [LeisureActivities].[dbo].[activities].[activityDate] > GetDate ()

GROUP BY [LeisureActivities].[dbo].[activities].[activityID],
         [LeisureActivities].[dbo].[activities].[activityName],
         [LeisureActivities].[dbo].[activities].[activityDate],
         [LeisureActivities].[dbo].[activities].[activityPlaces],
         [LeisureActivities].[dbo].[activities].[activityPrice];

As you can see this refers to 3 tables, activities , bookings and tempbookings . The tempbookings table also contains a tempReservedDate field which contains a datetime datatype, I need my SUM calculation for tempPlaces only to SUM those records that have a tempReservedDate in the future, those in the past just ignore (similar to how I'm already controlling the activities by displaying only those with a future date) the SUM also needs to group these by each activity.

I believe I need to put in my "WHERE" section something like

[LeisureActivities].[dbo].[tempbookings].[tempReservedDate] > GetDate ()

I just don't know where to put it to make it work without applying that to my whole query as it only needs to apply to the tempPlaces .

I hope I've managed to explain what I mean but please ask if it doesn't make sense, although I am aware that often you wouldn't format it how I have (with the [] etc.) but for the program that uses these queries it has to be done in this particular format.

Any help appreciated, thanks.

Answer 1

You need a conditional sum in the select clause:

SUM(case when [tempbookings].[tempReservedDate] > GetDate()
                then tempBookings.tempPlaces
           end) as FutureTempPlaces

Also, you should learn how to better format your code and use sensible aliases (such as tb for tempBookings ).