Ok, this is, then, quite an interesting idea. The problem is that you've got nothing reliable in your data to relate one date to the next (by the looks of it). You're only taking readings at roughly monthly intervals.
A good, purely SQL, solution to this would be to code a stored procedure that is guaranteed to hand out successive numbers, and then you can use that to do the arithmetic you've done already. You'd want another table that stores the current value of your counter, and your entry data process would get the next number for your next entry and update the table. You could do it by finding the maximum number already allocated in your table and add one (or whatever). If you're prepared to bet the ranch on having one reading every month without fail, you could find the lowest date and then generate an integer singly increasing index on month's since first date. That'd be two more SQL selections. The problem with what you've done is that there's no guarantee that it'll continue to work. It probably will, by the looks of it, but it's only a fortunate side effect of something that is not guaranteed. In a business environment you'd get fired for something like that, and quite rightly! In an amateur environment, you're getting away with it, which might be good enough for you. The next alternative is pulling the data in date order (yes, I know it's almost certainly in date order already, but if you don't make sure then you can never enter historical data [you're sure to miss entry for some reason some day]), and then run through the table doing the sum between last month's data and this month's. Of course, if you do ever enter data out of order the first strategy here won't work, or you'd have to manually reallocate your sequence numbers. Regards Mark -- For unsubscribe instructions e-mail to: [email protected] Problems? http://www.libreoffice.org/get-help/mailing-lists/how-to-unsubscribe/ Posting guidelines + more: http://wiki.documentfoundation.org/Netiquette List archive: http://listarchives.libreoffice.org/global/users/ All messages sent to this list will be publicly archived and cannot be deleted
