On 03/09/18 10:36, Svein Erling Tysvær setysvar@...
[firebird-support] wrote:

> I think the article Lester refers to may be the 'An auditable series of
> numbers' article which can be found on
> http://www.ibobjects.com/TechInfo.html.

THAT is the one ... did not think t check IBObjects archive ...

> Den man. 3. sep. 2018 kl. 09:58 skrev Lester Caine lester@...
> <mailto:lester@...> [firebird-support]
> <firebird-support@yahoogroups.com
> <mailto:firebird-support@yahoogroups.com>>:
>
> On 03/09/18 07:29, 'Christian Giesen' chris@...
> <mailto:chris@...> [firebird-support]
> wrote:
> >    NextInvNo = (SELECT MAX(INVOICE_NO) FROM INVOICE) + 1;
>
> Christian ... there was many years ago a very nice article on this very
> problem. The whole reason that will not work is when two or more people
> are adding invoices at the same time! My own system generates ticket
> numbers which ideally should not have gaps but if two counters press
> 'add ticket' at the same time they both see the same 'NextInvNo' ...
> I've added a couple of solutions which almost get it right, but just
> occasionally ... like once every few months ... we get two tickets with
> the same number created within 0.0001 second of one another -  what are
> the chances of that - obviously not zero :(
>
> Now a unique index should prevent that but in my case the ticket
> numbers
> start at 1 every day across multiple sites so the index has to combine
> several things and I never did work out who to handle the clash event.
> In your case you can make the index unique, but need to handle if two
> invoices are created at the same time ...

--
Lester Caine - G8HFL
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