On Mon, 19 Nov 2001 cnliou(at)eurosport(dot)com wrote:
> Then I am in big big trouble! Please imagine a very
> usual scenario:
> [example snipped]
I think you can do this as part of a trigger on PurchaseMaster and
something that doesn't do the subtraction if the subselect returns
a NULL in the detail trigger (or subtracts 0), not as pretty, but
it should function. The master trigger would subtract as necessary
for the details for the user.