Re: Next Serial value ?

Nils Myklebust wrote: > > On Sat, 29 Aug 1998 16:06:33 -0400, Eric Weaver > <eweaver@intelihealth.com> wrote: > > >Is there anyway to determine the next serial value to be used for a > >specific table (without selecting max(<col>)+1). I figure this value > >must be stored in a system table somewhere right? The server doesn't do > >the max+1 calculation each time does it? > > > >I need this value BEFORE the insert so that I can use it to create a > >hashed 24 byte code from it - then do the insert. Otherwise, I have to > >do the insert, get the serial value, create my hashed code, and then do > >an update. It would be more efficient to know the serial value before > >hand. > > If I understand you correctly you say you want the serial value that > will be used before you do an insert into the very table that contains > the serial column in question. > > Whatever you want there is no way standard way of getting at the > serial value that will be used. There may be some way to read it from > one of the sysmaster tables, but I don't know how. It's the column "sysmaster:sysptnhdr.serialv". I never ever would use this column - tomorrow Informix might decide to remove the column. > However what we do is to create a separate table with nothing but a > serial column. We do an insert in that and optain the serial value > from that insert in the regular way (sqlca.sqlerrd[x] x beeing 1 for > ESQL/C and 2 for 4GL or using dbinfo in a select statement). Then we > use this value to insert in whatever table that needs a modified > serial value (in our case simply a check digit, but it could be > anything of course). > > You can delete all rows from this extra table at any time to keep it > from growing. The next serial value is maintained outside the table > data as you asume, so there is no need for even a single row to exist > in the table between inserts. This idea sounds pretty good. Seems to work while "max(serial)+1" will not work if several users would try to obtain the next value concurrently. > Nils Myklebust > NM Data AS > Norway > E-mail: Nils.Myklebust@nmdata.com > FAQ at: http://www.iiug.org/techinfo/faq/faq_top.html > (Now with ODBC info under "Third party products".) Bye Stefan Weideneder