> On Sep 3, 2018, at 6:00 AM, 'River~~' river14ap...@gmail.com 
> [firebird-support] <firebird-support@yahoogroups.com> wrote:
> 
> Two ideas that should work on any SQL database so long as you never delete 
> invoices

Remember that a transaction can roll back, so delete is not your only 
challenge.  
> 
> I amNot a guru for this dbms so if a more specific technique is posted it is 
> likely to be faster
> 
> Note however that while my method may be inefficient, it is more likely to be 
> portable. You pays your money and you takes your choice
> 
> 
> With SQL and code in another language:
> 
> Start transaction
> Select max (invoice) ...
> Calculate next invoice 
> Insert...
> Commit
> 

That just narrows the window of chance that two transactions will see the same 
next value.  

> Or if you want to do it all in SQL then create a view that selects max 
> invoice plus one, and insert one row at a time from that view into the table. 
> The other columns would then be presented as calculated values 

I think that does nothing to solve the problem of seeing the same max value 
from two concurrent transactions. 
> 
> Either of the above are reasonably efficient if you have an index on the 
> invoice number, as firebird can easily find the first and last entries from 
> the index and iirr if the only column retrieved is the indexed value firebird 
> does not even access the table. 

Firebird does access the table to insure that the last index entry is a record 
version visible to the current transaction.  

Read the article in ibobjects. 

Good luck,

Ann

> 
  • Re: [fire... Alan J Davies alan.dav...@aldis-systems.co.uk [firebird-support]
    • RE: ... 'Christian Giesen' ch...@xt.co.za [firebird-support]
    • Re: ... 'River~~' river14ap...@gmail.com [firebird-support]
      • ... Ann Harrison aharri...@ibphoenix.com [firebird-support]
        • ... 'Louis van Alphen' lo...@nucleo.co.za [firebird-support]
          • ... 'River~~' river14ap...@gmail.com [firebird-support]
    • RE: ... liviuslivius liviusliv...@poczta.onet.pl [firebird-support]
    • Re: ... Gabor Boros mlngl...@bgss.hu [firebird-support]
      • ... Ann Harrison aharri...@ibphoenix.com [firebird-support]

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